You say 3.75W/gallon, you say two 55 watt T5 (dont exist) bulbs, which to me says you have a 29 gallon. Knowing for sure would be helpful because every tank has different dimensions and that has more effect on what you can have than you think.
Anyway, you should only count the daylight spectrum towards your wattage. Doing research I find that 55W is a common wattage for power compact that is 22" long, do your bulbs each look like a pair of bulbs instead of one tiny (dime in diamter) tube which would be T5? If so then they are PC, and PC isnt terrible but with 55W of PC (which isnt very intense at all) I'd say mushrooms and zoos are your limit, and I'd buy 1 coral and test to make sure.
What I say about watt/gallon not mattering as much is this. In a 55 gallon 4 foot long 18" high tank a 4x54 t5ho setup is considered "do almost anything, but make sure you put the SPS very high." math is easy to figure at just a hair under 4 W/g. I have a 175 MH on a 56 gallon, which is much taller (24 inches) and I'm pretty sure my coral choices are unlimited because the MH is more intense per watt than even T5ho.
Best of luck