grow tent questions

i recently decided to get a homebox s and i am wondering if i could throw a 400w or a 600w hps in there. it will be a cool tube. The dimensions are 2.6ftx2.6ftx5.3ft, it is recommended for a 250w but being a cooltube i was wondering if i could get by. i would really like a 600w in there but i only plan on doing like 4 medium size plants or 6 topped.
What would anyone recommend for a inline to take the heat from the cooltube on the 400w and the 600w. so basically what cfm would i need and is this even possible?

a 4 inch can fan is perfecto

will i be able to keep them within about 8inches? and how do you hook up a 4inch can fan to a 6 in cooltube wouldnt i have to go with a 6inch? im not doubting you i just dont understand

goto home depot and get a reducer 6inch fans are loud as hell and yes around 8 inches or so but get a glass sheilded hood reflector better than a cool tube