Cooling? 's and general design/layout

Ok so my room is approx. 60'' tall by 38'' wide and 18'' deep, I have a 600w HPS with a Euro reflector that has 6" cooling flanges. I also have a 6" inline duct fan rated at 160CFM, the reflector measures about 19" long by 11" wide and 7" tall, it is also sealed. I plan on putting the inline fan right near my exhaust point [unfiltered] being as it will exit via a chimney on my roof, and having a [passive intake??] to bring fresh air into the room and using the air in the room to cool the reflector?? OR instead of passive intake, using a small fan of sorts to bring fresh air into the room and have the same concept of the air in the room to cool the light?? My setup will be three stinkbud veg systems of my design that perfectly fill the footprint, each holding six plants and about 6to7 gallons of nutrients, I will harvest every three weeks or so. I plan on starting the flower when the plants are about 12" tall and working with clones for uniformity. This is my plan any info comments questions concerns or general input is much appreciated, I thank you all in advance.

I would filter the Exhaust air, and i would indeed exit it thru the chimmney (if possible). but you need a second lower intake(forced){fan} somewhere as well.