You may find that even with 3 of them that your par levels from mid-tank to the sandbed are a little on the low side for many SPS. I used a pair of AI Sol blues on my 120 (similar wattage I think?) and although things did ok - even a maxima clam on the sand, When I upgraded to a pair of Radion XR30 G4 pros the difference was noticeable. With the Sol's I was getting 100 or so par on the bottom. Now, with the Radions (after a lengthy acclimation period) the par level is 250ish on the sand. The clam, especially, loves the extra light.
To get the spread you will need, I am guessing that they will have to be 12-14" above the water. That's ok - it will help protect them from salt spray, and allows for easy access without having to move them.
hth
