Hydrofarm 8 Bulb T5 Light System

I just purchased 2 Hydrofarm 8 bulb T5 light systems. I plan on using these in a closet setup I made that is a 6x6 closet that has reflective insulation all around the walls. What im wondering is how many plants I can put under these two lights in this room and get the best yield possible? I plan on ordering tangerine dream seeds and I need to know how many seeds I need =D. Also, how do these lights compare to HPS? I live in a 1 bedroom apartment, is these lights going to make my bill go real highhhhh? Thanks alot! Hopefully I dident make a mistake by ordering these things.

T5's are easy. just put whatever plants you have directly under the size of the t5 fixture. so Im guessing 4'x2' each fixture which would give you a 4x4 footprint. If you used a flood tray you could put 4 plants for every square foot which would mean 128 plants in 4x4 flood tray if you went that route.