I think that 80 XML's will be overkill. You'll be at 400 - 500 PAR. There are some spreadsheets here for figuring out how many LED's and how much light, Hoppy's set one up.
I'm looking to do a similar build but am looking at ~20 XML's with a similar mix - about 10-15 violet, a few green, and about five red for full spectrum. About 100 PAR max with the lights 36 inches off the substrate, with the ability to turn the light down.