Best graphics card for dell optiplex 755

What is you currency?
What is your power supply capacity? brand & model?

I think OP's is "rs" for OP's money. And that isn't very much compaied. and what OP has for a system it would be a GT 430 or 440 on the nVidia side and on AMD the best OP can do is a HD 6670.

And that all depends on OP's PSU brand and watts. Anyway I wish OP good luck.

i am also a dell optiplex user the minitower has 305W PSU !!