Originally Posted by
Crossbow
I agree with CAT-THE-FIFTH regarding the PSU. If you need one, you'll have to factor in the additional cost into your budget.
You will also need to tell us about your PC case (ATX/mATX/SFF/slim-line?), as all the cards suggested are considerably long & broad. Plus the rest of your spec, especially CPU & RAM - you don't want to be running any of those GPUs along with a single-core CPU & 1Gb RAM.
Also let us know the games you're thinking of playing, & your monitor's resolution/make+model.