Well, I've been thinking about this more, and I'll have to agree with Snowy. Arson, wouldn't you think it'd be better to go w/ an x58 mobo with the LGA1366 processor interface so you can use Intel's newest processor? if I were you, I'd wait to go that route b/c you can actually save money in the long run, as the core i7 will be around for long time. I mean, you wouldn't need a new mobo or processor for maybe 2 years.
In the meantime, go ahead and buy that gtx 260 or 275 or 285 or whatever you want; you can hold off on the mobo and chipset until they're cheaper.
With the above setup, you should easily be able to score around 20,000 3dmarks. With your current setup, I'd say you're getting under 10k 3dmarks for sure (so less than half of the upgraded rig).