the $750 question

Should be easy.
Since your not planning to OC, a P35 mobo would do nicely I think, and those can be found fairly cheaply.
DDR2 is dirt cheap, get at least 2GB, 4 if budget allows.
The case is personal preference, but I'd find a nice looking Antec and you might even be able to find one with a decent PSU with it.
The problem comes when you start talking video cards. The 8800GT is always a nice choice, and they're mostly below $200 now. The 8600GT would also perform nicely for you I think and it's quite a bit lower I believe.

Hope this helps, I'll try to do a bit more looking around and post back in a bit.

If you not overclocking go with AMD.

Oki once I get home I give you some sugestions for you to concider AMD but like I said if you plan to OC than I havet o say you better of with Intel. The only thing that I found out over time that usually people that first ask me to build them a system that they will OC they endup trying few times and than going back to stock speed and never looking back. In my opinion OC is for hard core gamers that enjoy tweeking around. And as much I am for it I still don't find a reason for my self to OC unless I am only testing the pottential head room that the system is providing. Most of the time by the time I need OC I decide to build something new because there is so many great lower price better performance parts to choose from. Like with quads right now I don't really see a reason to getting one I would wait till the technology ages and go for it when is mature and pricess are resonable. Just something to concider.