[i7charlie]

I am thinking of getting another GTX 570 off of a friend for cheap and was wondering whether my Asus Z87-K Motherboard would support SLI.

 

[DeXel]

Short answer is no.

 

[smex]

The second PCIE slot is 4 x instead of 8x.. get one with 8x at the second PCIExpress
so it will look like 8x / 8x at the first and second slot.