If you're looking in the $200~$240 range the Radeon HD 6950 is very popular and is suggested in the THG article:
Best Graphics Cards For The Money: October 2011
Sapphire Tech lists the system requirements for it's
Radeon HD 6950 video and suggests a 500W PSU for a single HD 6950 system.
If you plan to overclock CPU & GPU, add extra case fans and a few more than the usual number of components you'll want to up the PSU a bit more besides.