Here you go!
Since you didn't specify many details in your post, I had to forgo any specific cases you'd like so you have to factor in that cost yourself. The build total above is $930, but after MIRs, it comes to $845. You can save some cash by opting out of getting a DVD drive, dropping the CPU cooler (assuming you don't OC since it's a budget board anyway), and getting a cheaper version of the 7850.
Also, you have to factor in the cost of the OS. You can play around with the consumer preview of Windows 8, or buy a copy of Windows 7 now since you'll be eligible for the $15 upgrade to Windows 8 when it's released.