For your size setup, i wouldnt recommend anything bigger than a 4 inch, i mean, im pretty sure my 4 inch serves my 4x4 just fine, but ive honestly never configured my inline fan to my tent by number like some people do, some people will size it by sq ft or some shit, i just grabbed at 4 inch and it seems to work. So thats what i would recommend but i could be wrong, im sure someone will rebound me if i am. But heres some ideas.
(These are links)
Expensive Setup:
AC Infinity - Inline Fan
AC - Infinity Carbon Filter
Cheaper Setup:
AC - Infinity Inline/Exhaust Fan with a cheaper, less beneficial controller
VivoSun - Carbon filter**
** Im not sure if there is a difference between AC Infinity carbon filter quality and vivosun.
Cheapest Setup: (I ran with this for the past two years, its stressful because the fan dies out all the fukin time, u get like 4 months worth of good fan CFM. Would not recommend):
VivoSun - Carbon Filter**
VivoSun Exhaust Fan W/ Speed Controller
Pocket Change Fan: I WOULD DEFINITELY NOT RECOMMENED, But i guess can be done for the time being?
PLASTIC VivoSun Exhaust Fan
Im sure there are other fans on amazon too you could experiment with, or i guess, just cut to the chase and end the issues before they begin with an ac infinity.
**Im also sure other people may have other recommendations for brands so if anyone has any brands or options to rebound this post feel free to post them. Like stated, id even love to upgrade further better myself if i can.
But i currently use the ac infinity and ive got to say, its like the smart phone of Exhaust fans.