i7-920 or i7-860, take your pick. Either will do what you're expecting the 870/950 to do.
Even if you're adverse to overclocking, current software based safe overclocks (ships with motherboard) will get it to 870/950 speeds w/o having to adjust any bios settings.
Your RAM is overkill also. Unless you plan on overclocking the X58 chipset has a maximum supported memory speed of 1033. 1333 for the P55.
G.Skill 2x2gb 8-8-8-24 kit for 96.99 for 1156
G.Skill 3x2gb 8-8-8-24 kit for 149.99 for 1366
No such 1156 motherboard as the one you've listed. Gigabytes SATA/USB III boards are P55a - ud3, ud3p, ud4p, ud6. And they all sacrifice any crossfire support for that capability. Look into the Asus p7p55d-e pro.
Meanwhile your 1366 board is a dated design that's been replaced by the x58a-ud5. It's a decent board. X58 doesn't have the pcie limits that p55 does so you don't lose the ability to crossfire/sli in order to gain usb/sata III.