Consider going the 8800GTX route, go short on the RAM, figuring you are not running 64Bit Vista, and focus on the video card, you can also buy more ram later and, if you want to go duel on the graphic card you already have a nice base with the 8800GTX.
I'm pleased with the nVidia 680i chipset, and you'll have the ability to upgrade to SLI later. Don't go SLI now, as it isn't yet cost effective. Spend your cash on the best single 8800 you can afford. Or better yet, hold out til Christmas for the 9800 GTX. :-) The games that require a new round of horsepower (like Crysis) aren't out yet. So hold out as long as you can, and you'll get more for your money.
We might get a new card from nVidia even earlier than Christmas.
Their VP of Investor Relations said they will have a new high-end card each fall from now on. That was in an interview a couple of weeks ago.
On the other hand, the OP seems to have the money for an 8800 GTX, but not much more. Nobody knows what the 9800 (or 8900, whatever) will cost in the first weeks, it might be a lot. It would kinda stink to wait 6 months and then get the 8800 GTX anyway. Also, nVidia has this nasty habit of not dropping prices when the new model arrives - the old model just disappears. I really don't know what the best solution is here...
OP: if you can, wait until the end of July for the Intel price cuts. With a little luck we'll know more about nVidia's plans by then.
Just an opinion, and something I failed to point out, if you go the 8800GTX route suggest going with the 831 and not the 881, IMO it is not worth the additional cost, as of today, for the additional clock speed.
I just built the system in my signature last week. Everything worked together without a problem. I just needed to manually set the RAM timing in the bios to 4-4-4-12. I would recommend this set-up to anyone.
P.S. The power supply was free, so I don't know a whole lot about it.