Good advice up there^. Unless you pick up one of the old X2's running at least 3-3.2ghz, you should set your sites on the new Phenom Processors. They perform better clock for clock, and they run much, much cooler than the old X2's, and use less power.
I had a 4600X2, running at 2.8ghz. I am now running a Phenom II 920 quad at 3 ghz, and the difference, even in games, is substantial. I have never ever regretted retiring my old X2 rig, or the money I spent on my new Phenom II rig. Oh, and just so you know you can trust me, I am running a BFG 8800GTS 512 OC, which is "comparable" to your 9800GT. You should expect nearly the same results.