I've never used intake and just count on my exhaust to pull in enough air , I run a 4 inch Vortex for veg but in my preflower tent I run a 6 inch and that thing works awesome in the 4 x 4 . I'd say go with a 6 inch and the aircooled 600 and that will be killer . If you have the funds also get a 8 bulb 4 foot set of T 5's for veg to help cut your power and run cooler in veg , it's nice and easy to swap out your lights when it comes time to flower .