An option would be a 3 foot long 6 bulb T5 fixture. You could grow anything you want with that. The standard ones don't dim or ramp. ATI does make a dimmable fixture. You may or may not like the look of T5, as not everyone does. The coverage and lack of shadows is best with T5, but the flipside is a flat look.
For LED on a 3 foot tank, you would be looking at 2 fixtures. I would probably try 2 x Noopsyche K7s. Kessils mentioned would work fine if you got 2. Radion, probably the XR15 models, would be popular but expensive. 2 of the Reefi Uno fixtures would be another option. Those or Radions would be a 1000 US dollars. Some kind of group of LED Bars would be an option.