I second (?) the AMD notion. As good and cheap as the i3-540 is, an AMD-based system will drop the cost even more. At the very least get a high-clocked dual-core and see if you can unlock the extra two cores. If not, pick up an
Athlon II X4 630. Don't get that 4650--your money is better spent elsewhere. A 5770 would serve you well, but as I am a bit of an NVIDIA fanboy, I have to recommend a GTS 450. Either the MSI Cyclone job or the ASUS DirectCU TOP (the factory-OC'ed one with the 952MHz core clock...that's a good one) will do you good. (If you want get a SLI-compatible board so you can double your graphics power later on... maybe
this guy.)
Get a better PSU for sure, and the Silverstone Precision cases previously mentioned would also do you good.
EDIT: Oh and G.SKILL RAM is a must. Get the Ripjaws with the red heatsinks, the ones with the CAS of 9. Those are good and cheap.