Personally, I'd go with two 3' T5 fixtures. I have the ATI dimmable sunpower and I love them. Everything grows under them. The hybrids are good too. Just more expensive. But I would recommend at least some T5 in there somewhere. Go 6 bulb and you will have a lot of different color choices. You can throw an actinic bulb, a purple, a coral plus, and 3 blue plus. That would make a nice colored tank and superior growth.
You mentioned two 24" fixtures. I wouldn't do it that way. I'd have T5 end to end on my tank. They don't radiate out much from the ends of the bulbs and I can't say that having a gap in between, even if you planned to hang some sort of a LED fixture in the gap, would look good.