I think I can answer both of your questions.
1) If you get a second identical fixture, you will be doubling your watts/gallon which would be excellent. I don't know that you will have enough room under your hood to fit two of those fixtures though . . . I have the same one.
2) There are some low profile MH
hoods. I just bought the Coralife hood that has 2 150W MH
bulbs and 2 96W actinic PC
bulbs. I am not positive that it would fit under your hodd but it might.
If you are looking for a second Current USA Satellite fixture, let me know. I am not using mine anymore and would be happy to sell it to you. It's 5 months old. I'm in Philly if that helps. PM me if you're interested.