As long as the RAM is DDR3 1866/1600/1333 MHz Non-ECC 1.5-1.65V then they are compatible with MB.
Then next question is how much do you want to spend on the RAM? Read the review they use the G.Skill 2666 MHz DDR3 memory. And if you want and use the memory finder too. http://www.guru3d.com/articles_pages/asus_sabertooth_z77_review,10.html
I think the 1866MHz RAM performance/price ratio is better than the 1600MHz.