Asus AMD R 7970 DirectCU II cf heat prob

I am planing to get 2 Asia and radeon HD 7970 on a Asus sabertooth 990fx r2 motherbord but reviews have said that you would a water cooling solution but do I actully.

no but if possible get the longest card supported by your case and get the shortest card and put the short one on bottom and long card on top try to have a 1 slot gap between cards so use the first and third 16x slot