If you want all T5s, you would want to have about 16 bulbs at a minimum for a LPS/softy tank, 20 would be more the ideal though.
Here is a tank similar to the dimensions you list ^^^ at 317gallons.
http://www.miniriff.de/Szczyra/szczyra.html
But personally, with a tank of that size, I think you can get away with alot less through the creative use of light movers for haldies/10,000Ks and blue T5s. If you did two 250wattDE halides with 10,000K bulbs, and decent reflectors (lumenarc DEs), you could put them on 3.5' light rails so they would move back and forth on the tank every 3 minutes or so. Even though these two lights would only be 500watts, their moving would give you better coverage, more natural light simulation (corals benefit from this greatly rather than a fixed, constant source), and double the effective coverage with those two halides. Then, use about 6 rows of T5s for 'filling' in the whole tank, both light/dark wise, and color wise. Three bulbs should be blue+, and three should be super actinics. This way, the moving halides will provide the 'peak' levels across the whole tank, but when they are not over a certain part, the blue and actinic bulbs will still be there to provide illumination for viewing, and supplimental growth/pigmentation.
If you want to suppliment with some daylight, you could make it 8 T5s, having a couple of them be aquablues or sun bulbs to make the whole tank less blue when the halides arent directly overhead. Either way, its a hard lighting setup to beat.
