Tom's HArdware (
www.tomshardware.com) is the place I'd start at for tests. Not that they're the best or greatest or anything like that, but they've had enough answers for me.
I'd bump the power supply up to 500W, and the memory up to 4GB. No, you don't really need them right now, but sooner or later... you'll wish you had them. Especially as frequently as you seem to upgrade