I'm installing a kitchen vent hood inline fan - what's the difference between using a Fantech FG 12xl and using a FKD 8xl? They both have similar specs, except the actual fan size is different. The FG 12xl is slightly cheaper and Energy Star rated. I'm installing this in a crawlspace that has plenty of room, dry, and in the middle of a long run of 10"x3" duct that is currently hooked up to an extremely underpowered microwave exhaust hood. Any thoughts?