bright what you want to do is look at gpu charts for the 7870 and 7950 and there replacement in the r line for amd.
on nvidia side your gpu lines up to the 770/780 line right now. nvidia this year is dropping there maxwell gpu (800) line. the first card was the 750ti because it was on the older larger gpu core. nvidia waiting for the foundry to be able to get yeilds up for the newer smaller gpu chip. the maxwell over the 700 line is less power and more works. the newer card going forward trying to be less power eaters. with amd cpu read up on the newer gpu cores used in the newer r line.