yeah. stick with the GTX...and I've always been a bit of an ATi fanboy. Bit dissapointed with the R600 thus far. If you are getting the 680i chipset then you will want the extra power headroom for a second gfx card in the future. The OCZ get good reviews so I'd stick with that. Don't forget to check webbies for efficiency stats though! As for the e6600 v e6700 argument, obv the 1x better multiplier gives you better o/c potential, but in most cases the e6600 can push just as hard with good memory/mobo combination, so im not sure its worth the extra cache. As you are going for such a hot system anyway, i wouldnt consider the E4* series.
Just out of interest, if you are spending on a nice 680i mobo anyway, have you considered the high-end asus options? seem to be the best o/c boards...