squirel cage fans are nice in large applications,but you also need 2 buy both flanges for them,also sold at home depot. i was thinking something like this.Hydro Wholesale offers Wholesale Hydroponics, HPS and MH Grow Lights, HydroWholesale hydroponic Supp: 6" TD Series Inline Fan, 312 CFM
.i use this just for my lights,and it hasnt had a problem keeping up.vents 2 600's and one 400 linked 2 gether andits just rite.