So I have began to propagate cacti from seed indoors. I am at month 3 now, and they’re doing OK under a floro. As they mature I am worried since my yard gets ZERO sun. I want to set up the closet in my office to be their home until I move in a few years. What Setup would you recommend?

I would definitely suggest a T5 for some of the reasons you suggested.

1) T5 would conserve more power unless you were growing them for resale

2) As you mentioned T5′s run a lot cooler and have high output lighting.

There are so many different climates that cacti grow in all I can say is “study your cacti and how much light and nutrients your variety needs to sustain a healthy life”.

If you offer me more information about the variety of cacti your growing maybe I can give you a little better information pertaining to your cacti.

Hope this helps and look forward to answering anymore questions you may have.