I was speaking from experience of upgrading from Q6600 overclocked to 3.6GHz to i5 2500K overclocked to 4.5GHz, my frame rate is more than doubled in online games that I play, despite I'm still on the same 5850. But the OP definitely need to upgrade his graphic card regardless, considering he got a 9800GT, not a minimum of 6850 or GTX460.
While is it true that bottleneck would happen, but the most important thing is try to balance it as well as possible. Pairing a slow CPU with a fast graphic card is the worst scenerio, as it simply won't use the graphic card to its full potential, and lowering graphic settings in game won't help much with frame rate; if graphic card was the bottleneck, people would at least have a choice to lower the graphic quality to trade for higher frame rate. Hate to say this, but your CPU at 4.0GHz won't be much faster than a Q6600 at 3.6GHz (if at all) in most games that use no more than 4 cores. Really wish you had asked for advice before jumping on Bulldozer.