it sounds like you have an awesome setup. how many watts are you running and how many btu's is your AC? is your AC dual hose or single hose design? i need to know the answers to those questions to get an accurate portrayal of your setup. i suggest getting a co2 generator as opposed to a tank/regulator because they are much cheaper and more efficient in the long run, as well as the fact that they raise less suspicion. you can buy one for the same price as a tank and regulator. i got my Green Air CD-18 for 150 off of ebay. look around...there are good deals. if you already have a tank, then its no biggie. it all has the same effect in the end right? if you use co2, you still need a way to vent the air in the room every hour, then you would need to refill to 1500 ppm. i run a 12000 btu AC to cool 1600watts of HID lighting, works like a charm and keeps the temps under 75 most times...