I have your standard 55 gallon 48"x13"x21" tank. Currently I've got 2 96w PC and 1 65w PC. I am thinking of changing to MH. I understand that you should have 1 MH for each 2'x 2' area. I am looking at the 175w 55K retro kit, ballast, bulb, reflector, socket, etc for $165. For this size tank, if...