GTS is still an awesome card, but it can't max out certain games, and probably won't play games at decent settings as long as the 260. I would get a less powerful processor (dual cores aren't even fully utilized, yet alone quads). I would go with a 3ghz core 2 duo and save some cash, then put that cash into the video card and get a 260.
What? In what programs are you seeing a near 2x increase in speed due to the extra core? Also, I can max out crysis with a 260 and core 2 duo @ 2.8ghz. The only people that actually need quad cores are developers and people who do mass rendering and video editing.