So, you have 500-600? Well, I would recommend you check out this build: http://www.tomshardware.com/reviews/phenom-ii-overclock... It's exactly what you need for your budget, with maybe a few upgrades. (Antec 300, 1TB HDD) But if you need a monitor, OS, mouse and keyboard, you need to up your budget.
XFX HD-687A-ZHFC Radeon HD 6870 1GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card $179.99
Patriot 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory Model PSD34G1333K $24.99
SAMSUNG Spinpoint F3R HE103SJ 1TB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive $99.99
SAMSUNG CD/DVD Burner Black SATA Model SH-222AB - OEM $17.99
I encountered a huge problem with the hdd while composing your system. ATM all of the hdds are double and triple the price they used to be. It is ridiculous. I suggest you wait a little bit and spend like 50$ for a 500gb drive as you should (Caviar Black/Samsung Barracuda 7200.12/Samsung F3) and put the rest of the remaining money on either a 6950 or a 560ti.
As things are with the hdds atm this is the BEST i could scrap up
I am having the exact same problem as the OP. I figured out a solution that seems to work for me, but it involves building the PC first and then adding a GPU and a bigger HDD a couple of weeks later once I save about $200. Maybe it will work for you too. I'm also hoping the price of HDDs will come down in those 2 weeks.
Western Digital Caviar Blue WD800AAJS 80GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive ($50)
APEX TX-381-C Black Steel Micro ATX Tower Computer Case ($25)
Rosewill Stallion Series RD500-2SB 500W ATX12V v2.2 Power Supply ($40)
Hanns_G HL227DBB 21.5" LED monitor 5ms Full HD 250 cd/m2 ($110)
This system is a total $525 shipped (everything from Newegg), but it includes a monitor (since you said you're starting fresh). Overall I think it's a decent starter build and since it has the Sandy Bridge with HD 3000 graphics on the CPU, you can actually use the computer without a GPU for the 2 weeks until you can buy your GPU (I will be getting a Radeon HD 6870 or a GTX 560 ti).
I hope that helps (any critique is welcomed, but I don't want to hijack anyone's thread).
go to high settings page(2nd page) that is enough , u can turn down 1 or 2 parts
dont change the cpu and gpu , ram also ok . just get a cheaper mobo(not recommended or get some gigabyte they are cheap in newegg) . ofc change the hd if u dont want or get a samsung hd cuz western digital are expensive (bcoz of thailand floods)
u will be able to play at high settings at decent frames
u can turn down cpu but keep it till i5 (min)
if u cant still make it get a second hand or a 550 ti or 460 768 mb