Iirc the 750i/780i are upgraded 6 series boards with pcie 2.0 being the main change from the 650i/680i range.Not according to EVGA's website http://www.evga.com/articles/401.asp
that board will not take 2 x 280 Gtx?
due to its having 3 Pcie slots: 1@ x16 and 2@ x 8
If you are getting DDR3 anyway its best to go the X58 route.
No, because that would require him having to buy a whole new cpu