These symptoms could be caused by a number of things. Obviously the first thing you should check is your driver versions and make sure you have the latest stable set, and also your DX9, make sure everything is up to date. Second thing I would look into is temps, which loks like you already have. Those could be lower, but shouldn't be giving you problems at those temps. Lastly I'd have to say it could be your ram holding you back. If you get some cheesey value ram, you'll know it. If your proc has no place to work (ie shitty ram) than you can't expect awesome performance.
I myself would have spent the couple extra and got the E6600, as it could possibly be the processor, but since the 8800GTX uses a new system where it actually takes a lot of the processing jobs away from the CPU, you shouldn't have a problem there.