Real temp issue.............

i'm having really bad temp issues and i was wondering the best way around it. I have a carbon filter fan blowing shit out and a oscillating fan in there but the temps is crazy high like 85-90. if its a shitty day and cold outside its usually ok and the temp gets down to 80 -78 but if it is a hot day outside i have to leave the tent doors wide open and that still only brings it down a little ( 82-87 ) and thats with me leaving my windows wide open. its only i have to wake up as soon as the lights turn on or the tent gets hotter than a mo fo! and its only a matter of time before they kill my babies. Does anyone have any links to some other grow rooms that i can get some ideas.
I'm using a 600w hps but i brought a 400w one hoping that it would bring the temp down but it never.
Also im a bit hesitent spending big dollars on temp controllers and heaters and all that cos ive spent quite a bit already and if i was ever to get busted by them po!po! they gonna take everything.
Any help guys...............

Get an air cooled reflector (either a cooltube or a supernova, summet like that) that should bring the temps down by about 4 or 5 degrees celsius. Thatll be the best youll get to be honest. And if you wana go furthur, get a small intake fan and ducting sucking cooler air from somewhere and pumping it into the tent/room. I have the same problems myself.

cheers pal!