Thanks for the very helpful answers! I think I'm going to go with the 750X. Just a follow-up question - my case (Rosewill future) suggests that I install the PSU upside down, with the fan facing the bottom of the case. This doesn't make sense to me, as the fan would just be blowing nowhere. Is there a reason I should do this, or should I just put it in fan facing up?
I own the case, the case itself has pegs that are a bit under one inch off the ground, so its blowing air through the bottom of the case. which is outside the case, so the inside of the case does not get warm