Here is a Google Spreadsheet comparing all the ATI cards.  It shows the best bang for the buck. (If you can find cards at those prices.)

https://spreadsheets.google.com/spreadsheet/ccc?key=0AsSwOT3E1XTGdGtpa1BQcmJLN2x6TG1MRmxzb29BeFE&hl=en_US&authkey=COWC8toK#gid=0