Absolutely DO NOT buy the Odyssea MH fixtures, no way. Their products are not UL listed, and not quality. I would be a little more lineant on their T5's, but absolutely not their MH
Look up a T5HO system, 2 36" fixtures will be better than 1 72" fixture for you, but that means you'll have to hang them. Look into getting 4-6 bulb T5HO system, much cheaper, energy efficient, run cooler, and can put out the same or better PAR than MHs. Try fishneedit.com, or a Nova Extreme Pro. If you are willing to spend a bit extra for a great fixture look into Sunlight Supply Tek lights. They don't come with bulbs and you'll want ATI or Giessman bulbs so factor that into you're cost with that fixture as well