Not sure yet, it depends on can the old rock push faster card before becoming too much of a bottleneck.
I know it can't push any 7900/680 level cards, but perhaps 7800/whatever-6xx-series-is-around-same-speed-when-they-come-out wouldn't be too much yet.
With limited budget the CPU upgrade has to wait at least 'till IB i5's are out and price settled to get max out of the bucks I got to spend
IB isn't worth it atleast not the current E1 revision. Basically same speed as the 2500/2600k and a lot more heat to deal with which means lower o/c potential. Your best bet is Z68/Z77 and 2500/2600k. 2600k is clearly a better choice thanks to HT and 2MB lager cache.
Hey CB, welcome back. I upgraded my Q6600@3.2Ghz to a 4.4Ghz i2500k, i used a 470 on both systems and the 470 was definitely held back somewhat, not by a huge amount, but enough to be noticeable. The difference in 3DMark11 is 1000 points using default settings. More noticeable was the minimum fps increase in several games, even @ 1920x1200. I was surprised to say the least.