70 Watt Metal Halides???

[eposer]

I'd just go with pc lighting on a tank that small. I'd be really worried about overheating a 5.5 with a halide, you'd need a alot in place for cooling & evaporation. With four 13W bulbs (almost 10W per gallon) or equivalent you'll be able to keep sps etc. no problem and you'll be able to have a glass/acrylic top so you won't need to worry about evaporation as much.
Plus the cost will be much less

Just a thought

Evan.