I have the 18" with 10 3w LED's. It has 3 blue and 7 white LED's. I am still scaping the tank and dont have water in it yet, but i think its too blue. Wish they had the light you're talking about in a 20" size.
Anyway, the light itself seems well made. I have one of mistergreen's DIY PAR meters on the way, so I will be able to give an idea what kind of out put these really have. Wont be exactly the same as the one you're considering, but should be a good reference point anyway.