hey fishguy, i'm looking at the "special twin tube glass top" here...I have a twin-tube flourescent fixture on my 20L (2x20), so its around 2 wpg. It grows crypts and stem plants, but very, very slowly. I have no co2, and I don't dose. if you go this route, get the special "twin-tube" glass top. I have the standard one, and the black plastic "flex strip" blocks part of tyhe light.
I think with the flat reflector of the Coralife 65 watt you would be OK, especially if you get some of the legs to pull it higher up. I have one on a 25 gallon tank setting on the rim and all is well. Its a new tank, but I've used this setup before with low tech - no problem.