Graphic cards for dell optiplex 980

Hi,

I am looking to add a graphic card to an Optiplex 980 SFF.

Any suggestions what would be the best available ones currently that would work?
Preferably without changing the 235 watt power supply.

What are the criteria I should be looking at for ensuring compatibility?

I figured out: Low profile less than 8 cm. I saw someone resolve a height problem by simply
cutting off a piece of the plastic holding the  harddrive.

If I would have to update the PSU (power supply unit), what are the criteria the new PSU should fulfill exactly?