I run a Mars Hydro FC-E6500 in my 5×5 and its a beast. You can get one on Amazon om sale for a little over $400 bux right now. Its 730watts but I only run it on full power for the last 4 weeks or so. I normaly fill my space with 8-3 gal pots or 6- 5gal pots and consistently harvest around a pound top nugs (2 to 3 oz per plant) and a couple bags full quality nuglets and shake for blasting and edibles. I use my 300watters for veg now only but had decent results flowering with them. Nothing like this big boy though.