that motherboard is alright. multiple grahpics cards are pretty useless but the problem is that you cant find really good motherboards with only 1 PCI express 2.0 16x slot so just buy it and nevermind that you have a second slot.
i dont quite understand you btw..
first you say that your onboard graphics chip keeps overheating and then you say that you have a GTX 260? WAT?!
also: if you buy that CPU then you need a better graphics card too because otherwise the CPU will never be fully occupied.
also make sure to buy a mugen 2 cpu fan. she is awesome and cheap
btw AMD's bulldozer 8 core CPUs will come in a few months and then you need a new motherboard again (AM3+) so i think you should waittttttttt