what are you planning on keeping, i'm pretty sure bridgelux would be fine for you, if you don't care too much about the slight efficiency difference. And the reason dimmer matters is, if you don't have the dimmer and you get cree, it could actually be too bright, and end up bleaching your corals. I have Cree LED's on my 18'' deep tank, and i never have them on 100%, the max i have them set at is like 70. The lights are about 10-12 inches off the water now. Even then i'm still having some corals fade a bit on the sand bed, but i think they're just getting used to the LED's. Good luck!