Help me keep my sanity

First off, Hi. This is my first personal grow, however not new to growing. I am new to growing in a smaller space from start to finish. And also enclosed spaces, as I usually work with a collective greenhouse. Moving for work for a few months and would like to build a flower box so I can keep my sanity.

I tend to over think these types of things, as I am sure you will be able to tell in the next few questions. But bear with me.

I have an area that I am building a box into. The walls will be modular and the box will sit 3" pan underneath. Grow area will be 4x4x6, not including the canopy area that will have the lights and ducting.

Questions:

I have an ePapillon 1000w and UI believe this could be too hot for the area. I will have quite a few fans built into the box (smell isn't a huge issue) and I can turn down the wattage to 600, but would like to know what everyone thinks about keeping it at 1000w and know how much air I should move. Maybe total amount of CFMs, ballpark of course.
So is this too hot? Could I counteract this with more fans or is it an asinine idea?

How many plants would fit comfortably? I know how big they get in the greenhouses, but just more unsure of how big they can comfortably get in that size area. Can you vertically trellis these plants? Would that lend me more room?

If you had this size room, what equipment would you like to purchase?

Thank you in advance. If I do decide to stay in this area I will have a 400sqft area.

FYI: I will have a seperate veg/clone room and am very comfortable with my dual Agroled T5/LED setup. Can grow each plant to any height.

Will this canopy area occupy the same airspace as the grow or will it be separate?
Use all 1000w if u can its a nice amount for that space. Extraction rates largely depend on intake temperatures but if I had to guess I would go overkill and get an 8" centrifugal fan and if u need to u can dial it down.
As far as plant count goes its upto you. Sog is the most efficient method but that could put you at 64 plants. Scrog is another way but you need to veg longer therefor u will need more veg space and this will take longer at first

The plants will grow as large as you let them...remember once you flip to 12/12 they will stretch a little before they slow down growth and start to bud. I tend to let them grow to about 1/2 of total size then flip, they will stretch anther 25% and over the course of flower grow another 10%

I run a 1000k watt in a 32x32 inch tent and have no issues with temp. I do have a titan temp controller that helps keep my temps in the 70-79 range but it warms up fast in there. I have a decent fan,

http://www.amazon.com/gp/product/B002ZJNW3Q/ref=s9_simh_gw_p86_d0_i6?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=desktop-1&pf_rd_r=14DPZDK5PZ92JGE0C19M&pf_rd_t=36701&pf_rd_p=1970559082&pf_rd_i=desktop

^^ thyis is the combo I ought not sure the exact CFM

what Blue Brother said is pretty accurate, all depends on the intake air temps, my basement is a cool 60-65 so I have no isses cooling the tent right off when the temp controller kicks on but if your intake temps are in the 70's you may want to look for cooler air somewhere.