I think, as i posted already, unless you are going sli/xfire the 750's to high. Its a great psu, but more power than you need, thus more money unneedingly spent.
the 550ti and above or 6770 and above would be great.
Which xfx 6770 are you looking at? I'd get the ZNFC model for the beter cooling, but it might not fit in your case.
If you lowered the psu, as 90% of people dont actual dual card it anyway, you could get a better gpu.