I've built some AMD based computers for recording. Worked out nicly with a custom 80mm CPU heatsink fan I make. You can buy heatsinks cheap that way too. Didn't know till I already made some though. Just quieter for recording than those regular 6000 RPM CPU fans.
I'm gonna build something in a few weeks for my birthday and here's the parts list in case you're curious:
-Tower case with clear side panel and decent 400 watt power supply. Extra glow fans for music creativeness.
-Biostar Nforce2 mainboard with onboard video/USB2/1394/NIC/audio (There's nicer ones like Asus and ABit brands out there but Biostar works good and cheap)
-AMD Athlon XP
Barton 2500+ Retail CPU. Comes with heatsink/fan but I'll use that for something else.
-60x80 CPU heatsink fan to be modded with an 80mm glow fan for low noise.
-Qty (2) 256 MB PC2700 cl2 DDR memory for 512MB
-60 GB Western digital SE (jb) 8MB drive
-Keyboard/optical mouse (both PS2, no USB)
-52xCDRW
-floppy
-extra IDE cable (motherboards usually only come with one)
You could typically build something like this for less than $650 without software. It's easy to build a computer, and the nice thing about a do it yourself is all the parts are standardized so it's easier to fix/replace/upgrade stuff.