My SPS would grow, but VERY slowly. Someone on this site once said that as a general rule, for sps double the manufactures suggestion. If they suggest two XR15s go with two XR30s. And yeah, $1600 is why I didn't try that experiment. Don't get me wrong, if you have the cash, Radions are super nice lights and extremely configurable. I think corals under Radion LED look better than under T5 as well.
That said, as an example I've had an Oregon Tort for two years. About 1.5 months ago I switched to T5 and in that time it has doubled in size. I'm also getting colors from my pink lemonade and other sps which I've never seen under my radions.