That really isn't a whole lot. You're going to want in the 6-8 bulb range IMO if you want to keep everything (anemonies, clams, LPS, and SPS). Aquactinics just released a 48" Constellation fixture that has 7 bulbs. That would be my first pick. A tad bit expensive, but one of the best T5 brands out there.
Right now you can keep softies with no problems, and the majority of the LPS in the top 1/2.
-Justin