I'd go with large plants, veg them in those buckets for at least 30/45 days or 2 ft tall (which ever comes first). I would go with at least 3 600/1000 watt lights (4 plants per light). I would also stagger the flowering and introduce 4 plants every 3 weeks. By the time the first are done you should be ready with the 4th batch of 4.