21" bulbs are the 65w bulbs, and only 2 of them over a 55...i'd say you're not gonna get a whole lot of growth. I'd go for at least a 2x96w fixture, but IMO...dont even look at pc's. Go right to t5's. A decent pc fixture is only like 40 or 50 bucks less than a good t5 fixture...so why not get the t5's? Way cheaper longrun, bulbs last double the time, cost less, and use less energy.
I got my t5 HO setup from reefgeek.com for 300, and its plenty enough for my 40 breeder. Before that i had 4x96w PC's and a fixture like that runs just a little under the t5's (if not the same).
You could add 2 54w t5 HO bulbs for now, and then later on get 2-4 more and grow whatever you want (assuming you get a good t5 fixture...i'd only go w/the icecap or the tek lights, none of the coralife crap
)
Also...fiji yellow leathers are a higher light coral. They do ok under lower light like pc's, but they do much better with brighter light. Just for kicks, here's my fiji yellow that i just sold yesterday..
Oh, but with the light you're lookin at now...you might be able to grow a few mushrooms down lower, and maybe some kenya tree up top...but in my opinion thats just a waste of money. That's gonna run you over 100...invest a tad bit more and you could get a couple t5's which could grow pretty much any softy.
