Ok I haven't read your complete mail, but here is what we have ordered as most-possible-but-affordabel workstations (sw development) in our Company (it differs from what you need, but still it should be a good base):
First, the case which is most important: Antec P180. It should be possible to fit that ASUS 2x Opteron board inside, cause ist is just a little bigger than standard ATX. Even EATX should fit into that case. It has the PSU below everything else, so it is thermally in it's own region, together with the hard disks. The cases side panels are two-layer plastic and metal which helps damping sounds. I don't know if extra damping material is available but the case is very quiet already, because it features thre 120mm fans which may be run very slowly, also depending on the mainboard's capabilities of course (thermal fan regulation). The power supply we used is a Fortron 400W model, don't know exactly which one, with a 120mm fan. Very Quiet. We have ASUS A8N-VM CSM as the mainboard, single socket 939 only of course, also µATX, but there's plenty of space left inside the case. We wanted to have Dual-DVI so together with a GeForce 6200 this was the cheapest, yet well-working solution (DVI from 6200 + DVI from onboard). CPU is Athlon 64 X2 4800+, under full load the system is absolutely inaudible in our office environment. Not sure for the living room, I haven't taken one there. The 120mm fans should have enough reserve for double CPU power to still run quietly, just make sure you use a fanless GFX card if possible. The K8T Master2 Far-7 you mention only sports RAM slots for one CPU IIRC, that is IMHO not a good idea as you loose half the possible bandwith and add a lot of latency for RAM access for the 2nd CPU in any case. Symmetrical RAM for each CPU is the best case under all circumstances. Hope that helped a bit. Did you want it really small? Not such a good idea for dual CPU I think, as you said ZmaxDP is not quiet at all for very good reasons. The P180 case is a midi tower, so you can put it below or on top of your desk. It's not too big and looks quite nice IMHO. My collegues were quite pleased, too =8) Darn, can't find which CPU cooler our supplier used, it's one of the big heatpipe towers with the fan on the side, not on top. If you take one, er two, of those, you should have a look at the airflow, depending of the socket direction it may blow 90° to the case's general air flow (front-to-back usually)... so long, Sönke