yeah, without good ventilation you're gonna have heat probs from the 600w alone. i've got a 460 sunagro and had to add a suck and blow system (2 daytons) to keep it cool enough when the doors are closed. luckily they're in a mobile home/trailer where easy access to the outside could be had thru the floor. but even with that once summer comes you won't have cool air to bring in and will need a/c...you'll have to either cool with your room a/c or bring in a portable. can you get by on less wattage? i think without a/c i think you're gonna have probs using that much...