I completely agree with stromgald about the noise problems, let me add my opinion about performance:
First off, how much/serious do you plan on gaming? You currently have alot of your budget in a high-end motherboard. From your selection of a 7600GT, I will assume that gaming is not the largest priority. I think a mobo with a single PEG slot will suffice. Something similar to these
If you game casually, I would stay with the passive 7600GT. If you want solid
performance, (high settings at medium resolutions), I would recommend a X1950PRO, which is about $200. (of course with a VF900 or Accelero X2 on it)
I also think that you could better spend your money by taking the Intel route. An E6300 will offer slightly
less or similar performance than the X2 4600+. I see Intel's future to be brighter then AMD's, so I would give up that fraction of performance for future upgrades. (You could easily make up the difference by slightly OC'ing the E6300) I also missed your CPU cooler. Most people here at SPCR would recommend a Scythe Ninja.
As for your case, may I suggest an Antec Sonata
? Or maybe a NSK 4400