You seem to have some restrictions. I know someone who has grown in an attic. If it gets cold.. consider that instead of investing in ways to heat the thing you will get more life out of your bulb and ballast because they'll be kept cool. Now, you can be sure that they will supplement some sort of heat. (we can work w/this more if you decide to do it)
For a confined closet, the use of flourescent lighting is recommended. I have seen AMAZING results during veg from flourescent lighting in confined spaces.

I have used 4ft T12 tubes/fixtures @ 40w warm white, but.. I've seen lots of these pics from CFLs as of late and am shocked at what they can do. It's a shocker.