The thing with Z97 m-atx boards is, if you wanne do 2 way sli, then you basicly block all pci-e slots. Gigabyte Sniper M5 has basicly the same problem aswell.
I dont think that there is any board on Z87/Z97 that has a full X16 slot on the bottom at 8x.
Till now i have only seen the EVGA X99 micro which has 3 pci-e 3.0 X16 slots. On which the bottom slot runs at 8x. so with this particular board you are able to run sli on X8 in slot 1 and 3. I cant think of any other option, as far as desktop boards goes.