I would go with 6 of each put both cool and soft on for vegetative growth, since all of the light spectrum's are important for a healthy plant. Then for flowering Ideal situation would be to switch to Hps, However if energy cost is a concern then I'd for flowering I'd switch/add to the big CFL bulbs They are between (actual wattage) 60watt and even up to like 200watt Ive heard, But even in the flowering stage I'd use both cool and soft white. As far as I'm concerned the more the merrier!