That really would depend on your tent size and what you are trying to accomplish.
by example, in the flower tent noted above- I have a 300w and a 200w <-- with settings,growth @67%, bloom @ 33%. This allows me to use the LED setting to help control heat. I choose to use a 4" fan/scrubber as it is quiet - rather that the 6" which would be too noisy for my room.
The veg tent and quarantine cabinet has 150w LED, and I add CFL/s for heat etc.
I get amazing dense quality buds.
So I am constrained by external factors of living in a old mill building condo, where every noise, vibration ,smell etc goes between floors and to each side.
If that were not the case- I would look @ LEC 315 for a single tent setup.