Nvidia recommends a 300 watt PSU for a 750 TI.
Link The max draw of a GTX 750 TI is 60 watts.
My HTPC with a GTX 750 TI (G3258), draws 114 watts max in 3DMark11. That was measured from the wall, so the PC is actually drawing a little less.
I would stay away from the few 750 TIs that require an additional power connector, but other than that it should be fine.