I had a 46 gallon with 2x96w PCs on it. Everything grew well. With a 3" sandbed, the tank is only 18" deep (personally, I would go ahead with a 4" to get the benefits of a DSB ) and I had plenty of light to grow both softies and SPS. I had good luck with digi and monti.
Anyway, I would recommend the T5s. They are supposed to last longer and have better output. I think that you would have heat problems with 2 MHs. My tank ran hot with just 2x96w PCs! 
Plus, there would not be an issue with center brace.
Bryan Tacker - North Austin ( 620 and Parmer )
110g RR > 2x250w SE XM 10k with 2x140w Super Atinic > Matt Sump / Fuge > Red Berlin Skimmer.