https://www.asus.com/Motherboards/Z87K/specifications/
CPU
Intel® Socket 1150 for 4th Generation Core™ i7/Core™ i5/Core™ i3/Pentium®/Celeron® Processors
yes to I7 4790k.
Multi-GPU Support
Supports AMD Quad-GPU CrossFireX™ Technology
so No to SLI, but yes to crossfire