Changed my hardware config, need help changing my overclock.

Question

About a year ago I completed my new OC system using a considerable amount of input here.  It has run well overall.  However, my original intent was to use the PC solely for productivity apps and internet access.  Recently, my XBox 360 died (you're shocked, I know) and I picked up Rome Total War to pass the time.  It didn't take me very long to realize the video card I was using wasn't adequate.  Here's my original system config (100% stable):
MSI K9N SLI Platinum nForce 570 BIOS 1.8
AMD Athlon 64 X2 5200+ 3.12Ghz (240*13) @ 1.45v
SuperTalent 1GB DDR2 800 445.8Mhz DDR2 (CPU/7) @ 1.90v, 5-5-5-15-20-2T timings
SuperTalent 1GB DDR2 800 445.8Mhz DDR2 (CPU/7) @ 1.90v, 5-5-5-15-20-2T timings
MSI NX8500GT-TD256E 576Mhz core, 512Mhz GDDR2
XClio Stablepower 500W +3.3V@30A, +5V@30A, +12V1@18A, +12V2@18A
I purchased an MSI NX8800GTS 320M OC to replace the NX8500GT.  The NX8800GTS uses a dedicated 6-pin PCIE power connector, while the NX8500GT does not.  In addition, the 8800GTS generates ALOT of heat.  The 8800GTS was increasing ambient case temp, which in turn was increasing core temp to the point that the system was becoming unstable after long periods of playing RTW.  I decided to lower my overclock in an effort to reduce voltages and hopefully reduce system temps across the board (I can't add anymore cooling, I already have 3 fans plus a Zalman CPU cooler).  Here's my current config:
MSI K9N SLI Platinum nForce 570 BIOS 1.8
AMD Athlon 64 X2 5200+ 2.99Ghz (230*13) @ 1.35v
SuperTalent 1GB DDR2 800 427.1Mhz DDR2 (CPU/7) @ 1.80v, 5-5-5-15-20-2T timings
SuperTalent 1GB DDR2 800 427.1Mhz DDR2 (CPU/7) @ 1.80v, 5-5-5-15-20-2T timings
MSI NX8800GTS 320M OC 630Mhz core, 930Mhz GDDR2
XClio Stablepower 500W +3.3V@30A, +5V@30A, +12V1@18A, +12V2@18A
Here's where my question comes from:
I ran Orthos small FFT test, priority 9 with the above settings for 12 hours -- no errors.
I ran memtest86+ test #5, 24 passes -- no errors
However, I cannot get the Orthos large FFT test or blended CPU + RAM test to run for more than a few hours without starting to error out.  I'm pretty sure the CPU is stable because of the small FFT test.  So I think the problem is my memory.
At 1.90v, the large FFT test errors out after about 30 minutes.  The blended FFT test errors out after about 4 hours.
At 1.95v, the large FFT test errors out after about 3 hours.  The blended FFT test errors our after about 6 hours.
At 2.00v and above, the PC starts behaving erratically.  It will freeze up sometimes, requiring me to pull the power and restart.  And sometimes it will just power down.
Should I just trust the first two tests and ignore these results?  I guess I'm not sure what to do at this point.  I accomplished my goal of reducing temps (almost 8C degrees) but I want to make sure the thing is stable.
Also, I asked this question a while back and got conflicting answers - is it better to have a high memory frequency or tight timings?  Because my cheap RAM really can't do both.

Answer 1

Here is what I meant by Fine Tuning or finding that Sweet Spot.
There are 36 different CPU Speeds and I figured 152 possible memory speeds based on figures I have seen here.
200 to 250MHZ FSB (10 MHZ steps I am guessing)
10 to 15 Multiplier
7-13 divider
308MHZ to 1071MHZ memory speeds
Many more are possible not just the 4 that CPUZ shows for your current settings.
Here are a few you might try with the 4-4-4-10 timings.
FSB   Multi   GHZ   Divider DRAM Freq.
220   13   2860   8   715
230   14   3220   9   716
240   15   3600   10   720
240   12   2880   8   720
250   13   3250   9   722
220   15   3300   9   733
210   14   2940   8   735
240   14   3360   9   747
230   13   2990   8   748
250   15   3750   10   750
250   12   3000   8   750
200   15   3000   8   750
230   15   3450   9   767
220   14   3080   8   770
250   14   3500   9   778
240   13   3120   8   780
210   15   3150   8   788
240   15   3600   9   800
200   14   2800   7   800
230   14   3220   8   805
250   13   3250   8   813
220   13   2860   7   817
240   12   2880   7   823
220   15   3300   8   825
250   15   3750   9   833
240   14   3360   8   840
210   14   2940   7   840
230   13   2990   7   854
Some are slower CPU clock speed than what you are at now but might Benchmark better at 4-4-4-10. Some have higher CPU speeds and might fail, but I listed them in case you wanted to give it a shot.  After all you might have hit the memory wall at 890MHZ and not the CPU wall at 3.12GHZ
Set memory volts to max allowed by manufacturer and have fun. You can lower them later in steps to fine tune.