I think it all depends on the resolution youre going to play... Dont buy a BIIIG display and you'll be happy with the results xD
Probably your computer can run any game till 1400x900 or something like it with high detail/AA/FPS, anything higher than this with normal or low details may run well also...
Crossfire is nice, but it gives some problems with titles that likes to use data of current frame into the next one... bkz... you know, the second card wont have the data needed in the local memory to process the next frame... Anyway, i think this is what causes those daaaamn micro stutterings with games that likes blur and offscreen drawing. (Anyone with crossfire + win 7 run Guitar Hero fine? I cant with crossfire on)
BTW, i got 2 Radeon 4770's and its perfect for my 22" 1680x1050 display I can play anything @ native resolution with 4xAA. (The best bottleneck you can have is your display HAHAHAHHAHAH!) >