Just in case it would help people looking at building or making build a desktop PC for Linux, I give you here the components in my new machine (bought in 2011). I have no problem installing and running Debian 8.0 (Jessie) or Debian unstable (Sid) (both in AMD64 flavor) on this box.
Actually I've been hit with Jessie by a slow boot problem, which is probably related to udev and the type of optical drive (Samsung SH-S223C SpeedPlus Serial ATA) on my box. To solve the problem, I had to modify (as root) file /lib/udev/rules.d/60-persistent-storage.rules and to run (also as root) the following command:
root# update-initramfs -u
Modification of file /lib/udev/rules.d/60-persistent-storage.rules consist in commenting out one of the rules in the file. It is explained on various Web pages, like this one or this one.
I made the computer build by Micro Logi, which seems to be a computer shop able to build your computer according to your desire. In particular, they could do the PC with the Silverstone case I wanted.
I really wanted this Silverstone Temjin TJ-08 Micro-ATX case because it is very short (depth: 378mm) and has good cooling power.
As far as the performances of the PC are concerned, I would just say that it is not suitable for gaming. A discrete graphic card is a must for gaming.
So, the components in the PC are: