Grow setup almost complete need help finishing.

okay so heres my set. its in my apartment bedroom and it's

2 ft deep x 3 ft wide x 6ft tall

im gonna be running a 400w hps with lumatek ballast.

also going to be constructing a DIY cool tube with the Pyrex bake a round idea.

now my question is what size inline fan to i need to cool the light effectivly.

at my local grow shop they have a 6 inch inline which pulls about 160 cfm it says on the box.

i will also be consrtucting a muffler box so noise isnt a issu

also i keep my beroom in between 68-73 68 being the low and 73 the high of the day. thats the readings i took from my hyrdo meter.

any help would be awesome.

anything for a 4in to a 8in will do