Personally, I LOVE
T5 lighting. There are more and more tanks using these types of bulbs and are getting just as good of results as
MH lighting. They are also more energy efficient.
If you have dough to spend, the Solaris LED lights are also pretty cool, and also very energy efficient. I find it difficult and confusing to talk about watts/gallon, because each tank and lighting system is soooo different.
If you're a handy person, you can even build your own lighting system with the different kits/components.
Shrooms don't need a ton of lighting, but if you're wanting to go with corals down the road, then why not start off the appropriate lighting?
Check out some of
these links, where there's hopefully a bit of information to get you going!