I have to disagree with the others regarding the bottleneck in your system. It's definitely the CPU. A 8800GT SLI setup is great for the games you want to run. But since I have no idea how CPU-dependent those games are, it's really a shot in the dark. If they're very CPU-depended, then you're looking at very low minimum frame rates. This happened with my dual-core Opteron at 2.7GHz playing TF2, L4D and GTA IV.
Simply, I'd upgrade the CPU to a Phenom II - any variety will do. Heck, even an Athlon II would be a good upgrade for games. You should check if your mobo can take the new CPUs through a BIOS update. Otherwise, you'll have to buy a new motherboard and CPU (and probably RAM).
As for automated overclocking - it isn't that bad if you're looking for a slight overclock, but it's generally looked down upon since you have no control over the settings. However, the parameters that auto-OC programs are generally on the safe side so you might as well try it out if you're not inclined to take time out to constantly tweak and stress-test.