if you already own i7 4770k then your only choice would be the maximus vi gene since rampage iv gene uses lga2011 socket which is different that that socket your processor use, also with the maximus has 8 usb3 and 6 6gb sata while the rampage iv gene has only 4 6gb sata and 2 usb 3 ports on the back panel.
I am considering the same options but am leaning toward the rampage since it seems to have better sound chip. at least thats what asus webpage states.