So thats a total of 15volts and thats not enough to keep your cabinet cool with the MH on. Now the Glass will help obsorb some of the heat. but your best bet would be to go to wal-mart and pic up 2 small fans for your out-take cause the 2 pc fans wont do much. Now using them to take out heat from you lamp is a good idea just give them a test run and make sure they dont melt if there plastic. Now for the passive intake method. It consist of a bigger/or more then one fan on the top and keeping 1/2 the size hole (PVC or a big enough plastic bottles rigged up on the bottom). for example if you have a 6 inch fan on the top youd want a 3inch PVC on the bottom with no fan. That will create a "NEGITIVE AIRFLOW" which will cause a breeze inside along with pulling in fresh air in/out. Now i will take some pics here in a few of my passive intake i rigged up. But i have to give props to my fellow members here whom helped me