Right Number of FANS/BLOWERS for Ventilation

hey all, this might be better suited for the Newbie Central but I've been trying to figure this out for a while, and I don;t want to order more stuff than I actually need!

Right now this is the equip. I've got:
6" Hydrofarm Daystar Reflector
600w HPS & 600w MH Digilux bulbs
600w Lumatek digital ballast
Secret Jardin DR150 (4'11" x 4'11" x 6'7")
Vortex 6" powerfan

Now what I'm trying to figure out is how many fans I'm going to need? I already have one 6" Vortex, thanks all!

I'd run the system, check the temps and then decide. There are so many variables yet unanswered....can you exhaust air completely out of room? If so, by adding one more item (carbon filter) you might be done buying.

Set-up sounds really nice. I would just add a carbon filter to the mix. Phresh Filters are the shit.

Yeah, exhaust will be going completely out of the room. My setup is a little strange, I really should draw up a diagram so that people will get the idea when I tell them about it. Going to start a journal later tonight, will post diagram and pics then of current setup