4 fans? Wow.  I'm only running 10 gpu, and 6 hard drives...maybe 1400w total.  The tent is in my garage.  So I'm hoping I can get away with a single 8" exhaust duct with a 450ish cfm fan that pumps it out through a vent in my attic to the outside.  Ideally I wouldn't need intake ducting at all (since i'm in the garage which isn't air tight), I'll just open up the flaps on the tent at the bottom.  Think that could work?

So I also live in Austin, TX, and am planning a setup using a grow tent.  @Saltyminer - in your experience, does simply pulling the air from outside and venting it to the outside keep the temps low enough?  How large is your intake and exhaust ducting?  I've been considering doing weird things like tapping into the air intake of my HVAC system to pull the cool air from, and then vent it either into the attic or to the outside.  Some tips from you guys would be very welcome before I ruin my house ha!