What size fan and filter?

So I have a 3x3x7 tent with a sunsytems 600w HPS and their large hood, 2.5'x2.5' I am growing 4 plants, very stinky, what size fan and filter should I use to control the heat and smells?

Anyone? My house stays below 74 but if I shut the door on the tent temps sky rocket inside it so I have been leaving the door open and now with the days getting longer I am worried about light creeping in so I need to get this figured out ASAP!!!!

I know I need either a 4 or 6" fan but I am tight on $$$$ but I don't want to buy stuff twice...

bump......

Go for the 6" are you using a air cooled hood?

Yes, hood has openings to make it air cooled as well as provisions to add glass, which I will be adding as well.

Sorry if it's bad form to link to another forum, but seems like good info.

http://forum.grasscity.com/grow-room-design-setup/375995-calculate-cfm-fresh-air-duct-size-your-grow.html