With that case, and that PSU you'll go through HELL managing the cables. I suggest trying to find a case that has cable management thought put into. A good example is the Antec p182 case. I personally built my computer in this case, and i tell you it's a dream to work in.
And get a modular PSU, again helps with cable management. I recommend any of the modular Silverstone PSUs.
Processor choice is good. However if you don't EVER plan on OCing your' better off with a higher clocked Dual Core. Namely the 8400 or 8500.
Cooler and RAM are good choices.
Motherboard is good, BUT it'll likely give you trouble if you plan on OCing.
A fast Hard drive improves load times, that's about it. So in my opinion it's no worth it.
And neither is the 9800gtx. The 8800gts 512 is a lot cheaper and performs very close to it, and beats in it some tests. If you want a high end card, your better of with the 9800gx2. OR waiting the new ATI boards are out in a few weeks. and maybe they'll be in your price range.