I run a very simmilar setup but with more than few fans (13) on a 420watt thermaltake td-420ad and it's going great. And i have an extra 512 of ram.
This is exactly what i run on my 420
2 WD 7200RPM harddrives
13+ fans
AMD 3400+ OC'ed to 2.47
CD Burner
Asus A8V OC'ed to 265ish
2x 512 meg ram
6600GT OC'ed