You should be okay with 2x 280Xs on a 750W PSU, just don't go overboard on the clocks etc
Also the RM PSUs aren't nearly as good as the EVGA PSUs, as the internals are poor compared to SuperFlower made PSUs (worse capacitors etc). They aren't bad PSUs, just not as good. Corsair support is good though
In the end, you/he will be looking at the case pretty much any time you sit at the desk so may as well go for something you like the look of![]()
Cheers..