Marineland is also coming out with a Plant Capable LED light. It's similar to the Reef Capable, but the lights are colored to be good for plant growth instead the blue/actinic look you get with reef lighting. It's supposed to be out this month.
For comparison, I have one 60" Double Bright light on my 55 gallon and I'm getting good growth from all of my plants. They are easy growing plants, but they seem to be doing great. I am tempted, however, to either get the Plant Capable system when it comes out or get another Double Bright and go "topless". The two Double Brights should put out about the same amount of light as one of the Plant Capable lights of the same length.