The current trend is: Plenum bad; DSB, good...

You might check out some of Ron Shimek's articles on a deep sand bed; there's a good basic one linked to a sticky in his forum on reefcentral. You'll learn a lot from that, I suspect.

Don't worry about your corals getting use to the halides; they'll do fine. Trust me on this. I moved every coral I had from an 18" deep tank with 2 55W P.C. to a 16" deep tank with 2 175W halides. Mushrooms, polyps, etc, all okay. They'll like it, I promise....

Matt