Post-Modification Problems: Hard Freezes. Kernel Panic?

Question

So, I bought a used Dual 867MHz MDD back in March and it appeared to be 100% functional. It even had gone through the PSU/fan exchange program (and was still slightly loud). Comparing it to a Dual 867MHz MDD I got just a week ago, it had a different PSU, all different fans, a different heatsink, different optical drive, and a better GPU (Radeon 9000 Pro 64MB as opposed to the "new" DP867 having a GeForce 4 MX 32MB).
About two weeks ago I overclocked the system bus on the first DP867 to 167MHz, thus bringing the CPUs to 1.08GHz. No problems there. I even changed the heatsink to a copper one from a DP1.42GHz FW800 model. Again, no problems. Pre-mod I had a 4x512MB config of PC2700 Crucial DDR memory at CL2.5. I replaced those with a 2x1GB config of PC3200 Princeton DDR memory at CL2 (2-3-2-5 to be exact) that have heatspreaders. I didn't change the GPU (though I have a Radeon 9800 Pro I'm going to put in once I resolve my problems... read on...).
Pre-mod and post-mod any RAM that is PC2700 or faster is showing up as PC2600 in System Profiler, which I find very odd. That same Crucial RAM is now in the un-modded DP867 which has a 133MHz bus and it, again, shows up as PC2600. I find this odd.
When I first got the now-modded MDD, I replaced the stock 60GB IBM HDD with a Maxtor 200GB drive that has a 16MB buffer. Works fine. All this time, though, it was on the ATA66 bus. Post-mod, I moved it to the ATA100 bus and then my problems began...
The machine would boot just fine. In fact, it would boot so fast I never saw the blue OS X loading screen. Kind of freaky. Then it would HARD crash in 1-5 minutes. The only solution was to hold in the power button until the machine turned off. Putting the drive back on the ATA66 bus didn't help. Back on the ATA100 bus, I could not re-install OS X from a 10.4.3 disc I have (guy who sold me the first MDD included that and iLife '06) because it couldn't verify the hard drive. Fortunately, I had so little on the drive, I backed it up to one of the spare 60GBs by putting them both in the second MDD and using Carbon Copy Cloner (great app!).
With the Maxtor on the ATA66 bus, I could re-install OS X, so I did. I did the Archive & Install so as not to have to deal with migrating user data. First thing I noticed when it rebooted into a fresh 10.4.3 was the CPU temperature at 60°C! As far as I know, these particular PPC chips max at 62. I freaked. I shut the machine down and let it sit for several hours before booting back up and patching to 10.4.7 and re-installing the Developer tools (and patching those to Xcode 2.4). This was a problematic process, interestingly.
My system is now back to the way it was pre-mod and though it's working a lot better, it will still occassionaly hard crash/freeze. Is this a kernel panic? When I shut it down and then boot back up it tells me I can send a report to Apple, but rarely does it show me the report.
Here're the things I think could be problematic or just some possible ideas:
1. I was under the impression that the 167MHz bus would recognize PC2700 speeds, but all my fast RAM shows as PC2600, which isn't even a real speed. This worries me a bit, as slower RAM doesn't play nicely with the faster bus.
2. The Acbel PSU doesn't have enough output. I believe it's 360W max (what an odd value). I changed all the fans to be quieter (and thus slower), but the 120mm main case fan had to run off of one of the 12V power leads since it uses too much power to go off the mobo's 2-pin lead meant for said 120mm fan. I also added two 60mm behinds the heatsink which are on a fan controller (also hooked up to one of the 12V leads - I only have one HDD and one optical drive, so there're lots of leads). I also plan on putting a Radeon 9800 Pro in, but now I wonder if this PSU just can't handle the added pull from the OCed bus (and CPUs) and extra fans (not to mention slightly more power-hungry 120mm fan).
3. The PC3200 RAM's 2-3-2-5 timings don't sit well with the system. The MDDs should be able to handle both CL2 memory and a 2x1GB config according to developer documentation for them.
4. I messed up the ATA100 bus during the modding, though with nothing attached to it, I don't see why this should be an issue.
5. Repeatedly opening and closing the case has weakened the thermal paste and I need to re-attach the heatsink. I doubt this is true, but you never know.
6. The PSU is over-heating? I know they get really hot and I'm in agreement with other modders that the MDD design is not thermally officient.
7. The CPUs are overheating. Temperature Monitor, post-mod and not including the post-OS X reinstall temp reading, has yet to show these CPUs hit 60°C. They get to the mid 50's no problem, and in fact, get to the high 40s very fast (and then VERY slowly rise to the mid 50s from there). Overall, then, the system is warmer than it was pre-mod, which I find odd considering the better heatsink and extra fans.
8. These processors just aren't 100% stable at 1.08GHz. It's possible if you consider the way processors are made and why they get clocked to the speeds they get clocked to. Or...
9. The whole CPU board needs more voltage, which would require some more soldering.
Lastly, this machine seems to, since the mod, be cursed by the PowerMac G4 "No Sleep For You!" Bug. No matter how you put it to sleep or wake it up, only the fans kick in on wake-up and none of the rest of the system. Holding the power button shuts it down, and after booting it tells me I can send an error report to Apple, and again it only occassionaly shows me said report. My father has a un-modded 733MHz Digital Audio G4 that can't sleep and my un-modded Dual 867 MDD can't sleep (it wakes up, then hard crashes about 5 seconds later).
Any information would be greatly appreciated. Not to knock the fine folks at MacMod.com, but I haven't been getting the kind of feedback on all of this I was hoping for there.
Here're my machine stats (pulled from an error log):
Model: PowerMac3,6, BootROM 4.4.8f2, 2 processors, PowerPC G4 (2.1), 1.08 GHz, 2 GB
Graphics: ATI Radeon 9000 Pro, ATY,RV250, AGP, 64 MB
Memory Module: DIMM0/J21, 1 GB, DDR SDRAM, PC2600U-20320
Memory Module: DIMM1/J22, 1 GB, DDR SDRAM, PC2600U-20320
AirPort: AirPort, 9.52
Modem: Dash2, UCJ, V.92, 1.0F, APPLE VERSION 2.6.6
Network Service: AirPort, AirPort, en1
Parallel ATA Device: Maxtor 6L200R0, 189.92 GB
Parallel ATA Device: PIONEER DVD-RW DVR-106D,
USB Device: Hub in Apple Pro Keyboard, Mitsumi Electric, Up to 12 Mb/sec, 500 mA
USB Device: USB-PS/2 Optical Mouse, Logitech, Up to 1.5 Mb/sec, 100 mA
USB Device: Apple Pro Keyboard, Mitsumi Electric, Up to 12 Mb/sec, 250 mA
Extra System Software:
Flip4Mac (latest version), Temperature Monitor (set to launch at log-in), Developer Tools (latest version).
Thanks in advance!

Answer 1

A few people out there have assured me that if I don't max out the system in terms of add-ons and things, the PSU should be more than adequate. I have 1x fan controller, 1x HDD, 1x optical drive, 1x graphics card in AGP slot that doesn't require an extra 12V power lead, no PCI cards, only two sticks of RAM, an overclocked system bus, and one fan hooked to a 12V lead rather than its 2-pin connection on the mobo (after discovering it doesn't run on said 2-pin connection). I've also taken out the case speaker to allow air to be pulled in through the top of the case.
I plan on adding two more fans to the fan controller (it can support 4). These fans will go at the bottom front of the case (under the face plate) and run at low speeds just to make sure the process of air flowing through the lower case starts off strong. So, two 60mm fans start it, the 120mm fan forces it past the heatsink (though as many probably know, not the whole heatsink - what a great design...), and then the two 60mm's behind the heatsink pull hot air out of the case.
Thanks for the info about System Profiler, Malcolm. I think you're right, though - if the CPUs were overheating, it would shut down. That's the whole point of the TAU's or whatever they're called.
I'm starting to think that either the 2-3-2-5 PC3200 RAM is suspect, or the processors are not stable at 1.08GHz. I'd downclock them back to 867MHz, but I think I need to buy some surface-mount resistors for that, and I really don't know what kind to get (as in, how many ohms).