An LED will only require 35 watt/sqft but 50 would not be bad. 50 watts is the requirement for HID (HPS) lights. Remember it is not the advertised watts but the actual watts used and the lumens produced that give you the numbers to go by.
I have a Mars Hydro Reflector LED that is 400 watts. I grow in a 2x4x5 tent and had no problem with heat. I had a 4" fan with charcoal filter. If you are concerned about heat, get a 6" or 8" fan that will exchange the air faster and thus cool the tent for you.
The 700 watt may be a problem but I wold think it would be workable.
The heat can generally be controlled by the exhaust fan. If it has a controller on it you can run it at a lower or faster speed, depending on what temp you want.
Hope that helps some. Jerry