Sadly enough, the cheapest i7 build I found online was from ibuypower of all the places; I built a 280 GTX, 6GB DDR3 i7 920 system for just over $1700 a few weeks ago for a friend, and no one else was even close...
My advice is to shop around for a while. figure out exactly what you want, find out via newegg around the price range it would be if you did it yourself, and find which vendor comes closest to that price.
I recommend the usualls, CyberPower, Ibuypower, Alienware, Digitalstorm, Velocity Micro, etc. Every once in a while, you can make a steal...