I'm just going to make this short and to the point. How well would a 4870 1GB run at 1920x1200 with a E8400 3GHz and 4GB DDR2 for games out now and those coming in the future? Would this be a pretty future-proof setup over the next couple of years for gaming?
I think you'll loose out with your Core 2 Duo. Intel is making a serious push for mainstreaming Quad Core cpus. Their next CPU line Westmere will be supporting 6 and 12 cores on the same 32nm die. More cores is the way the market is going however just like the Quad-Cores now the CPUs will be ahead of the software. Having a Quad-Core now will likely be mainstream in a year or two as more and more software takes advantage of multi-core cpus.