chtmatthew :
James Mason :
These are the cheapest:
http://pcpartpicker.com/part/msi-motherboard-h81mp33
http://pcpartpicker.com/part/asrock-motherboard-h81mhds
This would be better option for future upgrading of the processor/Crossfiring your cards:
http://pcpartpicker.com/part/msi-motherboard-z87g41pcmate
So I should get the MSI Z87-G41 PC Mate? So later I can upgrade? You sure it will work with all my other parts? Thanks.
Yes it will work. I gave you options besides the absolute cheapest because the cheapest option doesn't give you much choice in the future.
It would be cheaper to buy a new CPU (i7) and another XFX 7870 and crossfire it with your current one (make sure they're the EXACT same model) to increase the performance of your computer (older parts are cheaper in the future) without having to build an entirely new computer.