i think what mrsinister is referring to is the single core 4000+. back when i was shopping for a new system, most people were saying that for a GAMING only rig, a single core cpu was the way to go. now that's not exactly the story. with games starting to be made with dual cores in mind, you'll be glad you went with an x2. if you get the 4400 x2 you'll have twice the L2 cache, i don't know if it's worth it though. i got the 4400+ because i like to render video so i thought it might be the way to go for me.

i'm sure the antec TP II 550w will do you fine (the single 120mm fan model)

one thing you didn't mention, an aftermarket cooler. like os-wiz said, the xp-90c is a great cooler. i went with a larger, quieter version though (si-120 with recommended fan) http://www.frozencpu.com/cpu-tri-23.html it may not perform quite as well as the xp-90c but it keeps it cool and quiet.

i don't game much at all, so i can't help you with a vid card choice...

you're on the right track with raid 0 for windows. i tend to format about once a year too. just be sure to leave the pata drives out until after you have your OS installed. it ensures that your windows drive will be labeled "C" which makes things easier. and use the NVRAID raid controller, it's faster than the silicon image one. i am very impressed with the 2x74gb raptor setup i have. very snappy! just put your games on it and go. it'll give you about 140gb total. don't get the 36gb flavor, it's slower. then use your other PATA drives for storage. i linked a couple tests i ran with mine below..

i have mine setup like this:
a8n-sli premium
4400+ @ 2.5ghz
si-120 w/ panaflo L1a
2x1gb crucial ballistix pc4000 (250, 3-3-3-8 1T)
2x74gb raptors raid 0
2x200gb pata seagate drives
antec TP II 550w
6600gt
NEC 3500A
lite-on dvd/cdrw combo drive
antec super lanboy

here's a couple screenies to show the difference between a single 74gb raptor and 2 in raid 0
single 74gb raptor
2x raptors in raid 0