The 7750 doesn't maxout most games @1080p, in fact it's not a good card for 1080p.
I don't recommend going with a 7750, which the tdp is 55W.
It leaves still a margin, but with your cpu and other stuff, it might not function properly, like shutdowns in gaming.
If it's just for display two monitors and casual gaming, a 5450 is enough.
For gaming the 7750 is better, but for a 300w psu.