duct fans are about $40.00 each and move 500 cfm easy if your not pulling it too far.
I use several od these. but for the $$$ your talking you can cet a "VORTEX" duct blower (but use it to pull) which is very quiet and long lived 10 yrs. I think.
blowing heat will leak out but sucking (pulling) will not leak and is more efficent.