Think about getting this:
Motherboard: ASUS P8Z77-M-PRO mATX $128
CPU: Intel i5 3570 $207.00
GPU: nVidia Gigabyte GV-N650OC 2GB GTX650 $149.00
PSU: Coolermaster GX Power 650watt $92.00
Case: I don't know what type of case you want so i thought it would be best if you found one by yourself.