Wow, nice keyboard.. I didn't even know it existed until now and it seems to be nice...
Anyways, with my experience with my CM Storm, a typical keyboard supports 6KRO over USB and can do NKRO on PS/2, assuming that the matrix or whatever it's called is well designed to have this capacity.
Now before you go and buy a USB to PS/2 converter, do you even need NKRO?