Hi there.. as a general rule of thumb think about 50 watt (wall-drawn) per square-foot.. so in case of a 4x4 that would equate to around 800 watt.
I personally like quantum boards (but also have a COB), because they have a nice spreading and create less hotspots than if you use multiple cobs.
just look at the ppfd charts for the various lights, and see if you still get sufficient light nicely spread over the whole canopy without too many hotspots.
happy growing