Fan replacement for MDD | Amount of airflow really needed?

Question

Hi,
I am thinking to replace my noisy PSU fans with new ones. However, those old Delta Fans seems to have pretty... high-end specs what comes to airflow (38 CFM) and therefore the noise level (47dba). I have been working with computers pretty long time and I have never seen a computer which actually needs that much cooling just for PSU so I think that less is better in this case.
I thought that I replace them with 12 CFM fans (with only 20 dba each) or then again I am looking an alternative methods to create a somekind of airtunnel into that PSU by adding second cooler + pipe to the front of PSU. Is there anyone who has actually modded this PSU with this level before?
Also I am thinking to replace that 120mm cooler with 50-60 CFM cooler.
Howabout adding small cooler to the CPU heatsink?
... Desperate? **** yeah. I could use my MDD to blow leaves from my front yard!

Answer 1

If you aren't using NAP mode, I certainly recommend it in order to get that baseline temperature down. My MDD 'idles' i.e. email/web at around 39 degrees C. And for me, it has not introduced any instability.
I also applied the fan kernal extension mod (see URL below) which spins up the main fan at a lower threshold:
http://homepage.mac.com/paul74/MDDFanExtensionMod.htm
The extension mod doesn't let my MDD go above 56 degrees C and having the quieter Panaflo means I barely notice the difference anyway. This only tends to happen if I'm doing something CPU intensive like video transcoding using Handbrake.
Further improvements I've recently undertaken are:
1. Replacement of the passively cooled Radeon 9600 Pro with an Nvidia 7800 GS (BFG). While this has a fan, it only spins at full whack during boot and then calms down - it isn't noticable during normal operation.
2. Replaced the original IBM system HDD with a 'whisper quiet' Seagate (or WD - I forget which). I did this as the original IBM was pretty noisy - something you only notice once you've got rid of most of the fan noise.
3. Flipped over the PCI slot cooler. The intake for this was on the top. I removed the body from the metal slot mount and turned it around so that rising hot air is more likely to be captured. It is definitely pushing out hot air now.
I still plan to make a few further changes. I recently moved the speaker (now fixed to the interior 'ceiling' using bluetac). Considering mounting a fan where the speaker used to be to suck air in for the PSU and graphics card intakes.
I'm also still considering some exit fans between the CPU heatsink and the rear case.
Regarding the optical drives, I removed the stock combo and replaced it with a dual layer DVD/RW taken from a Lacie external FW unit I used previously with my eMac. I kept the original in a safe place in case I ever need it though!
In terms of OS X support for third party optical drives, I hear cough that it may be possible to update the firmware so that it is cough cough seen as a Superdrive. Thats just what I hear anyway.
Powermac MDD   Mac OS X (10.4.9)