If you plan on getting a Quad, and your ambient temperatures are high, go water cooling.
Right now it's the main focus of my next build.
My CPU: Probably E2140 or E4300
My GPU: 7950GT 512
Instead of upgrading the CPU and GPU, I'm going water because I'm in California, it's very hot here and I don't want to go Quad before water, as Quads are really night and day with water.
Your OC'ability and over-all system stability/performance/noise will all be drastically better with water. The GTS can play anything you throw at it, I don't think the $180 upgrade would be worth it.
Thanks for all the input guys as you have made my decision quite a bit easier. I don't need the best nor do I feel a need to upgrade right away, but I am sure I'll be thanking myself down the road when the new stuff comes out.
I'll probably get a little added performance from my video card upgrading to a quad core as well.