Strapped has some good advise. You should reconsider the fans on the intakes. It can only be the cause of issues down the line. Positive pressure introduced into the cab or grow room is never a real good idea. Putting fans on the intakes isn't going to be the best bang for the buck anyway. I would consider increasing the exhaust "suck" instead of intake "blow". Any failures at all with the filtered exhaust, and the little fans at intake can blow funk out of every nook and cranny the grow has.
Your passive intakes should be plenty big. If the temps were in check with the carbon filter disconnected, then reconnect it and add exhaust fan pressure. (increase fan size or CFM)
what if i created more negative pressure in my cabinet by blocking off some of my intake ??? wouldn't that in theory remove more of my air & heat without having to up my cfm's ??? or would i still have heat probs cuz of the 250 watter ?
i've got a pretty good negative pressure now cuz you hear the air sucking through the door when its open a crack or as i'm closing it you can hear it then too .
maybe i should just leave it alone ..... if it ain't broke don't fix it huh LOL .