It will, but for how long? I have no idea. It's nominally a 400w unit, but it's made for a Pentium 4 type system. Most modern system draw more from the 12v rails and your 12v rail is only 160ish watts at best. 60-70 of those are going to the 750ti. That leaves 80-90 for EVERYTHING else on the motherboard.
I wouldn't use it.