I'm running my XR15g3 with wide optics @ 18k spectrum (100% UV/RB/B -- 25% W/R/G), 65% intensity, and added 2x24 ATI Coral+ Blue+ and everything is loving it. (SPS Biocube).
Gotta say, the SPS all responded to the T5 immediately. I'll either add another 2x25 or replace the Radion with an ATI 4-6x24. I love the Radion and I'm sure the G4 is better, but w/e makes my tank happier is the priority.