Graphics card for Dell Optiplex 790 SFF ?

Hi,

I want to upgrade the graphic card for my pc with the configuration as below:

Dell optiplex 790SFF *

core i5-2400 Pro (Sandy Bridge Quad-Core 3.10GHz, 6MB cache) 

RAM 4GB (2x2GB) DDR3 1333MHz 

HDD 250GB 7200RPM 2.5" SATA 

DVD 8x Max Slimlide DVDRW

* Intel HD Graphics 2000,

Dimensions (H x W x D) Inches/(cm): 11.42 x 3.65 x 12.28 / (29.0 x 9.26 x 31.2) 

It has a half height PCIe x16, and the power supply is only 240W.

I don’t know selecting which graphic card can fit in Optiplex 790SFF and work fine with PSU 240W .

This is details my mainbroad : http://www.redplanettrading.com/Dell-D28YY-0D28YY-Optiplex-790-Small-Form-Factor-SFF-Motherboard.html