I run a 2x4x5. Easy asnwer: 315 LEC, get a fixture with a separate balast that can sit outside the tent. Yes, you will need at least a 4 inch inline fane sucking air out the top of the tent.
At least, that's my set up and I love it.
Alternatively, you could do 2 smaller LEDs, and you could grow some righteous weed, but you will still need to extract hot, humid air when you have big, flowering plants trying to finish and not get moldly.