I have 4 - 24 watt T5s running on an IceCap 660 ballast. The lighting is so intense that I have to warn everyone in the room before I open the canopy so I don't accidentally blind them! Seriously, I have been extremely pleased with the set-up (thanks a bunch Eric and David!).

Bottom line: I have only 96 watts over my 20 gallon tank, and I have seen enough growth on my SPS corals to confidently recommend it to others.

Perhaps Eric (or another knowledgeable lighting person) could step in here to explain more about watts vs. PAR...