John;

Not sure you're asking for this sort of advice, but if you're wanting to set up a fairly small reef tank I'd use something different than the 55 gallon. That shape tank is very difficult to light with any efficiency and aquascaping is tough. It's really long and skinny; good for florescent tubes, not good for mh bulbs. If possible, go with a 36" X18" tank instead; either 45 breeder or 58 gallon. Then you can use 2 mh bulbs to get really good light throughout the whole tank; actually 1 400W bulb with the right reflector would do the job. Everything about this shape tank is better for a reef; rock placement, water movement, sand bed size.

If you must stay with the 55 gallon (48X12) I would not spend a lot of money on the hood; either do the 4 X 55W PC bulbs you're thinking of and limit the animals you keep, or find mini-pendents to hang over the tank so you can use them when you switch to a better tank shape.