I've got an arcadia light unit for my freshwater setup, it's just a ballast and starter with two cables with end caps.
The end caps can be mounted anywhere, they can be screwed, bolted or stuck in place and can be used with varying different bulbs and sizes.
Mine is called an Ultra Seal Controller but of what I don't know, as far as I'm aware, the power output isn't adjustable.
The lighting is very good and the bulbs are fairly cheap at ?10 for a 15inch bulb.
The lighting set up cost me ?13 for the bulb and ?30 for the controller.