Fan Intake/Exhaust Help

The space I have set up for flowering is 7x7 I have a 170cfm and a 424 cfm fan. I have 2 400w HPS lights for the time being. Should the bigger fan be used as an intake or vice versa thanks in advance

I also have an inline (6" ducting) fan and 6" are the outlets in my reflectors (HTS Euro). What would I want to exhaust air away from my lights with? The 424 is 6" and the 170 cfm is 4".

"vise versa"... x3..