It depends. You could add RAM and a new processor as well. If you want to upgrade, I am going to put a CX500 power supply just in case. Its not that much more expensive:
PCPartPicker part list:
http://pcpartpicker.com/p/jiuU
Price breakdown by merchant: http://pcpartpicker.com/p/jiuU/by_merchant/
Benchmarks: http://pcpartpicker.com/p/jiuU/benchmarks/
CPU: Intel Core i3-2100 3.1GHz Dual-Core Processor ($109.99 @ NCIX US)
Motherboard: ASRock H61M-DGS Micro ATX LGA1155 Motherboard ($44.99 @ Amazon)
Memory: Corsair XMS3 4GB (1 x 4GB) DDR3-1333 Memory ($19.99 @ Newegg)
Video Card: Sapphire Radeon HD 7850 1GB Video Card ($176.97 @ Newegg)
Case: Antec Three Hundred ATX Mid Tower Case ($39.98 @ NCIX US)
Power Supply: Corsair Builder 500W 80 PLUS Certified ATX12V Power Supply ($51.98 @ Newegg)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($15.99 @ SuperBiiz)
Operating System: Microsoft Windows 7 Home Premium SP1 (64-bit) ($92.60 @ Amazon)
Total: $552.49
(Prices include shipping, taxes, and discounts when available.)