Okay. I'm making this thread as the 'ultimate PC' configuration. Something I'm laying down right now is that it HAS to be an AMD processor. (Sorry, Intel lovers).
I'm looking for EVERYTHING. Case, Mobo, PSU, CD/DVD drives, even twiddly details like the thermal compound (although I think Arctic Silver 3 is what everyone will agree is the only way to go) and the 1.44MB floppy. (YES, YOU STILL NEED ONE!)

It would be great if you could find a mobo that has VERY FEW features. Modularity is key for this one, and onboard stuff is too redundant. HOWEVER, there ARE some things that I think should be on the mobo. Ideally, those would be a gigabit Ethernet controller and a 4- or 8-port Serial ATA controller with RAID-0, 1, 0+1, and 5 abilities. The more 64-bit PCI slots, the better, and 8xAGP would be pretty rockin'. I'm not sure if any manufacturers are doing this since it's not ATX-conformant, but if there is a motherboard and case that has an extra slot next to the AGP with no PCI connector (for, for example, the big fuggin fan for the GeForce FX), that'd be groovy as well.

In the hunt for this elusive ultimate PC, there should be a good balance between power and noise but without any kind of water or freon cooling systems. (In other words, just air cooling.) Preferably all the components would not need any modification, but some small modding would be acceptible.

I am not certain about the implications of using dual- or even quad-processors (if such motherboards exist) since many times load is not distributed evenly even though it should be and they would require 2 or 4 times as much airflow from the CPUs (noisy!).

Case noise padding: yes!

Oh, the mobo should support, if at all possible, ECC-registered RAM and 333/400MHz bus speeds.