You intake should be twice the size of your exhaust. Is the exhaust from the tent exiting into the room or out of the room the tent is in? You should be able to make this setup work.
Cobs give you a lot more usable light than HID's, better spectrum, more efficient and less heat. I'm using 300 watts worth of cobs that replaced a 600 watt hps per 4 x 4. Check my link below for my cob lights