If you simply want more output running the same footprint, check out 315w CMH Elite Agro setups. They're great for a 3x3', will pull less than your current 400 and yield like a 600, less heat than both and incredible flowering capabilities, drawing ~345w total @240v, 385w @120v. Check out my (sig) thread for more details. Have a 3x3 running right now, plus another over a single blue dream in a 24" x 36" footprint.