The EVGA board will work just fine on no OC or even slight OCing. I run an EVGA X58 motherboard and have no issues. It will work with an i5 750 and DDR3 RAM. You can go with either 1333 or 1600 with the tightest timings.
You can run either ATI or Nvidia in a single card setup, so you can use your ATI 5870.
So this new system could be more efficient than my other "AM3 ASRock 890FX DELUXE3 board with a Phenom II 965 BE and 4Gb DDR3 1600Mhz OCZ AMD BE", with this board and the i5 750? even if the i5 750 is at 2.66Ghz and the Phenom II 965 are at 3.4Ghz ? (i think the ram will work the same)