Currently i have an AquaticLife 4-Bulb T5 24" fixture with (2) ATI blue plus bulbs and (2) ATI special blues.
I am extremely happy with this set-up, and I'm having no issue even growing SPS.
KcTx (with a 54) has the same fixture but the 30".
I will say that if I had the money, and may still do it soon, I would opt for either the Vortech Radion LED system, or the AI Sol LED system. I think they are superior and cost efficient in the long term.
I believe the 24" version of what I have is $250ish, and the bulbs are $80ish. Total approximately $350. The AI Sol is $400 but no bulb replacements, and the radion is $700, with more features, but again bulbs last an extremely long time.