Uhm... It's a close call for a 5750 or anything on that league. I wouldn't recomend a card with auxiliary power for that PSU.
My suggestion is: Get a little more money for a good PSU (around 40-50 bucks more) and you'll have a good rig for quite a while.
If you can't wait nor can't get more money, then i recommend getting a 5670.
You can browse on this link
and look for a card that you like.