IMO you can build a much better system with that budget. A few of the parts are outdated and overpriced and some are just nasty (PSU).
CPU: AMD Phenom II X3 720
Overclocks great being a BE and there's a good chance it will unlock into a quad core
Mobo: Gigabyte 790GX AM3
RAM: 2x2GB G.Skill DDR3 1600MHz
Don't bother with DDR2 now, it's actually risen above the price of DDR3, so what's the point?
GPU: Powercolor HD 5770 1GB GDDR5
Faster than the 9800GTX+, uses less power and supports DX11
HDD: WD 500GB
Disk drive: Samsung
Case: CM Elite 330
This is a personal preference, but even when it's cheap you need functionality, something those newegg branded things don't have.
PSU: Corsair VX550W
Do NOT skimp on your PSU. How long do you think a cheaply made PSU with poor quality components is going to last? And what happens when it does go bang? Does it have built in protection for your other components? It's providing power to your whole system, a cheap PSU can easily turn into a very expensive mistake.
Total comes to around the same as what you chose.