You would be fine with just the 4*54W and run them 8 hours and that would be plenty... You could always get 6*54 and run 4 of them for 8 hours and have a hour or two noon burst. I think i recall Tex Gal in her journal having 5 *80watt and ran three of them for 8 hours or so and used the other two for a couple hour noon burst. She has a 125g i believe and her plants are amazing. I just did the numbers and that would be slightly higher than her lighting so if you go that way you will have to make sure that your ferts and everything is in balance before you start using the othet two bulbs. A lot of people would prolly say that that is to much light, but i always like to have options just incase i want to up the lighting at some point in time.
I think that tank is 48" x 18" x 24" high, right? So the lights would be about 24 inches from the substrate, if the fixture sits on top of the tank. In that case 2 T5HO lights, with the typical single tube reflectors made of highly polished aluminum would give enough light to grow almost anything. For more flexibility a 4 bulb fixture, hanging a foot or so above the tank would be best, so you could lower it a bit to get higher light intensity, or raise it a bit to get lower, and you would have great uniformity of intensity. Six bulbs would be too much.