A HIS Radeon HD 6990 4GB for $499! I found this while browsing through MSY Auburn's clearance list. The 6990 is usually around $750 which makes this a great bargain. The 7970 is about $700 at most stores at the moment and the 6990 beats it at almost every benchmark. The downside to the 6990 is that it is a dual GPU card which can run into problems multi-GPU related and some people complain of micro-stuttering.
I do not know how many more they have left (less than 5 for certain) so calling them first is advised. I believe this is to make way for the AMD HD 7xxx series of GPU which are slowly being introduced this year.