I think the slightly deceiving claim refers to the non-resonant chassis itself, rather than it's ultimate quietness in use (it's supposed to contain noise very well, but the power supply fan spins up audibly if you start putting hot components in it):
http://www.silentpcreview.com/article146-page1.html
I also own a couple Zalmans and agree that they are quiet, but most definitely not silent. Some over at SPCR have replaced the fan with something quieter like a Nexus 92 mm fan (search the archives there - it involves cutting away most of the plastic frame of the replacement fan, then drilling two small holes in it to mount it to the Zalman heatsink). There are also software fan control programs such as Speedfan and Motherboard Monitor that allow you to set a higher target cpu temp so that the fan spins slower and presumably quieter.
I belive they also say that the Thermalright Si-97 is the best socket A cooler and is supposed to work very well with undervolted quiet fans:
http://www.silentpcreview.com/section10.html
If you are trying to achieve true silence (and don't need massive amounts of hard drive space), a suspended notebook hard drive might work out really well for you (picture of suspended hard drive here:
http://www.silentpcreview.com/article228-page3.html ; just note that I think you need some special power and IDE cable adapter).
You may be able to get an used mobile Athlon XP (from an European seller) here?:
http://forums.anandtech.com/categori...=45&entercat=y (does your Gigabyte mobo have cpu multiplier and VCore settings in BIOS?). The mobile XPs are just supposed to be regular cpu's that have been selected because they function well at lower voltages. You could just try underclocking your current cpu and see what it is stable doing (don't know if there are any hazards to doing this, so do this at your own risk).
There also are a lot of international forum members at Silent PC Review, so a WTB ad here
http://forums.silentpcreview.com/vie...569a503c4f2a3c might be fruitful for you.
Also, the Nforce2 chipset in the Biostar M7NCG is supposed to be better than the Via chipset in your Gigabyte mobo. If you can find a revision 1.0 M7NCG, I believe it has IEEE in addition to Soundstorm audio processing unit, in addition to the require cpu multiplier and vCore adjustments in BIOS.
Hope this helps!