I installed one gt 730 gddr5 1GB on my friend dell optiplex SFF with 235W PSU on it. That pc has the old lga 775 c2q with 4GB DDR2. So I will say any good brand 250W-300W PSU, you need more head room, because dell pc PSU is good.
I got a 300w one and i saw on NVIDIAS web page that they say 300w im just curious if Asus tuned it does it require a better supply since i cant find the solution online