Whats the best graphics card for me?

depends on your psu... but you should be able to stick pretty much anything into that system.

most people overestimate the power draw of their system... and you can get a 4 pin to 6 pin adaptor, and use any gpu with it (heck my old HD 3850 came with one, as did my more modern HD 5870... which was nice because my psu at the time had only 1 6pin as well)

not a huge fan of the psu you've got but you should be fine with anything up to a 7870/660.. heck, depending on the psu's reliability you might be able to get a 7970 onto it.

so yeah... i wouldn't worry too much.