Re: DDR3-1866 not supported by CPU
I have that same memory, and while I am using it in a Z77 extreme4 mother board and running it at 1866, if you got a good price on it, I'd keep it.
If I recall correctly, I had to use a XMP profile in the UEFI to set the memory to 1866, otherwise it booted up as 1600. BTW, if you needed to, you can slit that memory up and in to two PC's and run it as 8GB per PC in dual channel (it's only going to be dual channel no matter if you install 2 or 4 sticks anyway).
ASRock Z77 Extreme4 ASUS Sabertooth Z77
G-Skill 16GB Ripjaw X DDR3 1866 G-Skill 8GB Sniper DDR3 1866
Cooler Master 692 II Advanced USB 3.0 Cooler Master 692 II Advanced USB 2.0
EVGA GTX560Ti FPB EVGA GTX560Ti FPB
Corsair HX850 Silver Plus Cooler Master Silent Pro 850
Crucial M4 128GB SSD Samsung 830 128GB SSD