Optiplex 990

New to the forum so bare with me, I have a Optiplex 990 SFF that I need to put a graphics card into, as you know this model has the graphics built into the motherboard (which is going bad) rather than replace the motherboard how good of a graphics card can I put into this unit...note: the original power supply a 240w was replaced with a 300w sometime ago and has been worked fine.  I know I will need a low profile card that is no larger than 6.2" x 2.5" so could I put say a GT730 2GB DDR3 card in this unit or maybe a GT 730 Low Profile 1GB GDDR 5 ? both these cards should fit size wise.

Any help would be appreciated. Thank You