Low Profile Graphics cards

Your best bet is an ATI 5570. It really doesn't have much, umph, but will let you play some games at lower res or settings. Older games shouldn't be an issue, but more modern games will need to run on low for the most part depending on resolution.

There isn't much out there in the low pro market, and especially with stock PSU's.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

You can thumb through the reveiw for an idea of what to expect:
http://www.tomshardware.com/reviews/radeon-hd-5570,2552...