Excellent advice there. Let me add a few:
The Striker Extreme and the P5N32-E SLI are identical, except for a few things that the Striker has and most people don't need. If money is an issue and you are trying to decide between those two then definitely go with the P5N32-E SLI and not the Striker.
The QX6700 is overpriced. A Q6700 (available July 22) will cost $530. I believe the QX6700 is easier to overclock but that's the only difference AFAIK. If you need the rig sooner consider a Q6600. (I'm waiting for the Q6700.)
If you really want SLI do it with two GTX cards. If you can only afford one for now that's also fine. I'd go with the 850W version of that PSU for 2 GTX cards. 750W is fine for one GTX.
Will you overclock, or are you concerned about noise levels? In that case you need a good after-market cooler. Plenty of threads about this subject in this forum. I'm getting a Zalman 9700, but there are some other great options too, some cheaper.
Edit: get 4 GB of RAM if you're planning to install Vista at some point. Right now you'd get a better experience gaming on XP, but one of these days both Vista and nVidia's drivers for it will become very good, thanks to all these enthusiasts doing beta testing and reporting the bugs