What can I grow under a T5 Hydrofarm 4' x 4 bulb light fixture?

[seaj]

I'm planning my first indoor grow shelf for some mini phals, paphs, african violets and some small aquariums. The plan is to contain everything on one 5 shelf 48"x24"x72" Gorilla Rack, though I may need to remove one shelf to fit everything.

For the low light plants listed above I want to use four 48" T8 32 watt bulbs + reflectors for each 48"x24" shelf. Does that sound like the right amount of light?

Now onto the title question: Will a T5HO Hydrofarm 4' x 4 bulb light fixture allow me to grow orchids with an medium-high light requirement? I want to add some mini dendrobiums, mini oncidiums (Twinkles), and possibly some mini cattleyas to my collection. Or would I be better off getting the 6 bulb fixture instead? I've never grown plants under lights before so please excuse my ignorance and attempt to simplify matters.