Well fist im gona say, good idea with the T-5HOs! I think that for your size tank, not sure the lenght...30-36inches, the 4x36 would be awsome. One thing though, do you know if the fixture has individual reflectors or one single one. If you can, you should check out
ReefGeek > Aquarium Supplies for Marine, Reef, and Saltwater Aquariums They have a great selection of T-5HOs Fixtures.