@ BJonson:
Thanks for the pics! I wonder, how big the max size of thickness would be for this small fan. It seems there is 5-8mm more space.
@ harrymatic:
42°C in summer sounds great and it is still that loud?
If one can believe the fan specs and compare them to other fans, you could use this list to find other fans (people have used fans with lower airflow, though).
MDD Single CPU (suggestions by aquamac):
taken from here
http://aquamac.proboards.com/thread/1174?page=1#8403 , where there is also an info how to build a cooler ATX PSU into the flat housing of a MDD-PSU and make room for other fans. (I've also seen people cut of a part of the PSU metal at the end and put 1 80mm fan there, instead of the two 60x25mm fans, I am not sure though how that does match up with the PCI cards.)
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PSU - stock 2x Minebea 2410ML-04W-B60 5300 RPM 25CFM @ 38dBA
New - Startech FAN6X25TX3H 5000 RPM 26.5 CFM @ 30 dBA
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Door - stock Delta AFB0612HHB 4500 RPM 17.3 CFM @ 35dBA (60x15mm)
New - Startech FAN6X1TX3 4000 RPM 15.9 CFM @ 28 dBA
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CPU - stock Papst 4212H 3400 RPM 108CFM @ 49dBA
New - Scythe Slip Stream SY1225SL12SH 1900 RPM 110.31 CFM @ 37 dBA
MDD DUAL CPU:
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PSU: 60x60x25mm. stock Delta fans, model AFB0612EH, fix at 6800rpm, constant 38 CFM, 47 dBA. ---> 64m3/h
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Door: 60x60x15mm ???
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CPU: 120x120x38mm, under 69cfm at low speed, stock Delta AFB1212SHE variable speed fan that can spin up to 3700rpm with a maximum airflow of 152 CFM and a noise level of up to 53 dBA
OR SHORTER (for cfm devide m3/h measures by 1,69):
MDD Single CPU:
60 x 25 = 42,25m3/h / 38dB(A)
60 x 15 = 29,24m3/h / 35dB(A)
120 x 38 = 180m3/h / 49dB(A)
MDD DUAL CPU:
60 x 25 = 64m3/h / 47dB(A)
60 x 15 = ?
120 x 38 = (ca. 110-) 258m3/h / 53dB(A)
It is said, that the door fan (60x15mm) is not a real noise factor.
I have two fans in my list that would fit there, though (one being very rare to find):
Fander Roxo Ultra Silent 60x60x15mm, 2300rpm, 31.6m³/h, 16.8dB(A)
Xilence WhiteBox SlimLine, 60x60x12mm, 2100rpm, 50m³/h, 22B(A) (COO-XPF60S.W)
For my Sawtooth I tested a supposed quieter 120mm fan to meet the 146m3/h (86cfm and 32dB(A)) by Xigmatek, which I found louder than the stock one (it has 150m3/h /90cfm:
XIGMATEK XAF-F1255
airflow (m3/h): 90cfm (as stated by manufacturer)
noise (dB(A)): 26max (as stated by manufacturer)
subjective noise: loud
That info doesn't help you anyway, since the Single CPU MDD has a max airflow of 180m3/h, but if you want to try a lower airflow fan, like others have done, you are warned that the Xigmatek is not worth a try (unless case design has a vital effect on sound design as well...

)
Edit:
on the 9800, go to themacelite. There are some cards that either way support fan speed control or can take a special rom that allows fan speed control. If you might want to reflash it or search for another 9800 model or a better stock cooler that someone pulled of a 9800 with one of the special coolers.
Here is the buying guide with all 9800 cards (including not working ones, that are told to avoid) and remarks about what ROM (size/version) can be used and the features.
http://themacelite.wikidot.com/flasher-s-buying-guide-9800
Only working 9800 cards
http://themacelite.wikidot.com/9800-working
Remark on additional cards, that won't work (scroll down)
http://themacelite.wikidot.com/ati-radeon
This intertesting about flashing and moding ROM chips
http://themacelite.wikidot.com/navsubcat
Other than that browse through the index on the left side.
In the compatibility chart they notice that a 9800 won't work in a Sawtooth, because there is no 2xAGP 9800, but there are, you can find them in the working 9800 cards guide. (I just metnion it for future reference, I know you will be able to use a 4x/8xAGP 9800 in the MDD).