These have 17 between them but only 600- 720w rms.30-40 on 4x4ft tubes would be easy.
I've thought of sandwiching peltier cooling between the cob and cooling tubes for unsurpassed efficiency.the draw back being more heat and electrical draw on the set up overall.
Either way watercooled will easily out perform any aircooled set up and it remotes the dissipated heat to a desired location with readily available plumbing pieces!
I'm planning on eventually prototyping water blocks purpose built for cob grow lighting with parabolic reflectors and varifocal lenses. I'll have them cast and machined to fit common Cree,Vero,citizen etc holders.......that's the dream anyways....