My specs:
CPU: AMD Phenom II X4 3.4GHZ
RAM: 4GB (I can expand this if needed)
Power supply: 500W
OS: Win7 64-bit
Cooling: I don't know the specifics of my cooling system, but heat won't be an issue. My pc runs cold to the touch, even when gaming, and is full of giant empty spaces

How I want to run Skyrim:
Anti-aliasing: none
Resolution: 1400x900 (or thereabouts)
Everything else: better than the PS3 or 360 versions
fps: at least 40 frames per second
Please reccomend the best possible budget graphics cards. I understand if I'll have to settle for less, but I'd like to get as much out of my pc as I can, for as cheaply as possible. Thanks.