Two of those in a 22 liter Rubbermaid grow box, two 6500k for vegetative and two 2700k for flowering, would be nice in place of a 70w HPS if that's all you could get. I'm guessing that 65w gives out close to 7,000 lumens, right? Two would give out at least a little over 12,000 initial lumens and maybe about 10,000 mean lumens after it's been on for about five - six hours. Maybe not the best light penetration, but it'll get you a good half ounce a plant. Shit, you could also toss a 5.0 or 10.0 UVB light in there during flowering with the two 2700k's, that'd up the quality of the THC a little -- at least enough to make up for the lower yield.