Ok, here's my input:

PSU: It's fine. My Phenom has been crunching on 350W without trouble for well over a year, and it has a GT9400 for graphics, 2 harddrives and 2 optical drives. But unfortunately not OC'd, so don't know how that will affect it. I'd think it's fine though.

My view on the case, get one you like if you're going to put it in anything, cuz you shouldn't ever have to replace it, just upgrade what's in it. (But I also don't spend too much on cases... just a decent one with airflow, leave the side off.)

I'd be tempted to throw an old 512mb stick on top of that 1gig for the ram.

Harddrive: I'll second D_A, if it's not too much different, go WD.

And since it's a dedicated cruncher, you probably don't need a Optical drive, just borrow one from another computer to install OS and you're good.

Oh, and definitely get an aftermarket cooler. You're system will be more stable and last longer with less problems.

Just a side note, I think you'd get better PPD/$$$ going with one of intels new i3/i5/i7s. If you overclock it, (according to snoro's numbers anyway) a i3 will match, if not beat this in output and an i7, while a little more expensive will kill it. I know it's a bit more of an investment, but I've done both. (Phenom then i7) and the extra was more than worth it in my opinion. But I'll leave that to you, no pressure either way.

Hope that helps a little!