Replace i5 750 with i5 760. Newer/faster model, price is usually almost the same.
Skip the sound card unless you are using the PC as a sound studio. For gaming and video playback, onboard is plenty good.
Use the saved money on the sound card to upgrade the 460 to a 1GB RAM model. It is significantly faster than the 768MB model.
902 is one of the best aircooling cases available. Twin 260s wont cause serious overheating if room temperature is reasonable.
Look for Cas7 timing RAM at around the same price.
Unless you have an application that you know needs more than 4GB RAM, you arent likely to need it.
For overclocking you need a good CPU cooler like a Xigmatek Balder, Xigmatek Dark Knight, Sunbeam Core Contact Freezer, Coolermaster Hyper 212 plus or Scythe Mugen 2 (SCMG-2100). All are under $50 and will let you overclock to 4GHz without heat issues. You might leave Turbo boost on and just overclock to 3.2 GHz. That seems to be a sweet spot for power/heat/performance on the i5 750. The 760 might go a bit higher with turbo on and no major voltage increase.