so, on max your computer should eat about 200-220W, add another 50W for safety measures, which leaves us at about 105-125 W free for the graphic card...
if you have a 6pin connector>
AMD> AMD> 7750 /if your PSU doesn't have the 6 pin power connector/, 7770 /if it does/, even 7850 could fit /if you're feeling lucky as you'll be stretching it a little bit/
nVidia> GTX 650 TI /with 110W, this card hits the exact limit, TI BOOST is out of question, it is more power hungry than the 7850/
also - pep out your ram to 4-8 GB, if you already haven't.