The 680i and Q6600 is a good bundle at a good price. If you're willing to spend $50+ on cooling, buy a Zalman CNPS9700 Heatsink for Socket 775 (Intel CPUs). It's probably one of the most well respected air cooling systems on the market, barring some of the more expensive Thermalright stuff. If you're not going to be overclocking much or don't have a big budget to spend on a heatsink, get a Cooler Master HyperTX 2 (around $25). Both those parts are compatible with your MB and CPU.

The 8800GTS is still a strong performing card. If you want some extra grunt, buy an identical model and run them in SLi. Just make sure your PSU can handle two cards in SLi mode. You might scrape in OK at 450w, but it depends on the other components in your system.