I'm thinking an i7 system for around $800-$1000 (assuming a i7 920 and a GTX 260 (216)). This leaves you with upgrade options later, unlike all LGA 775 builds.
It'd be real hard to get an i7 system with a gtx260 ~$800.
i7 - $280
gtx260 - $175
Board - ~$250
RAM - ~$90
That's pretty close to $800 right there. This doesn't include a psu, case, hard drives, opticals, OS.....
$1000 can build an i7 system. But it will be a stripped down build.