The 640AAKS is the best desktop drive on the market right now IMO. It's half the platters with more space than all the other drives at $0.17/gb. So it's faster, quieter, and more reliable than any drive in that class. Note the 500AAKS & 7200.11 have four platters and the 640AAKS only two...
I have 3 WD640AAKS in this setup with no problems. I could not get XP SP3 to recognize Matrix Raid without major hassle. Jmicron worked but was not a major improvement, only +10mb/sec over a single drive. Vista 64 was a super easy install without having to pre-format. With ICH9R you can add...
This is the best bang for the buck I could find:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820134642
Avg. Read 18mb/sec
Avg. Write 8mb/sec
So a single 1gb file takes 2mins to write.