Hey Iceman...
Check out this thread I stumbled on the other day. Its from a different pot website, but it has great info for buying the right size fan for your cabinet size.
You need to be aware of the standard of exchanging the air in your cab 5x per minute....so if you got a 6 cubic foot area cab, you need to have at least a fan rated at 30 cfm.
The link:
http://www.greenpassion.org/f45/what-size-vent-fan-do-i-need-intake-area-size-3704/
Thanks Hal! That's good to know! That means I don't need to get new fans I just need to mount them and cut holes for exhaust and intake cuz I have 2 4" Axial fans that are 110cfm and the flower cab is 2.4 sq ft so I will have perfect air flow asap!