Hey bro I have a 2'x4'x6' Sun Hut brand tent which actually measures about 3.5'x5.25'x7'. I would highly recommend this. I use a 400w cooltube inside. Great minds think alike huh? lol
If you stick with the 400 watter heat won't be as much of an issue, but believe me it WILL still be an issue. I have a portable a/c unit that I back up to the tent to keep my temps low since I'm in TX (right now at least...). A 600 watter will get you better buds, and the 600w unit is overall the most efficient of all the different size ballasts.
With a tent you're going to need an input fan and an output fan, and don't go any lower than 6". 4" ducting is a waste of time. You need 2 inline fans with a tent or otherwise you'll get the 'balloon effect' if the airflow is not stabilized properly.
Anyway, there are a lot of options out there and I've tried several of them. I would never again buy any brand tent other than Sun Hut. Not only are they the best made with the best dimensions and the most exhaust ports, but they're also the cheapest out of the name brand tent manufacturers. And remember to get the silver-lined model.
Here's a pic of mine that sorta shows my setup in the tent. You can see the portable a/c in the background.
