More lumens means better growth. The 600 should help plants grow a little faster and fuller its a high intensity discharge setup and it will better penetrate the canopy to the lower branches. The only thing about high pressure sodium bulbs is the spectrum that is put out is closer to 2700 degree color temp. and thats better for flowering. Metal halide bulbs are closer to 6500k which closer represents the sun light in the optimal growing season were as hps bulbs represent the late days of summer with the orangish-red skies. Personally I would use the HPS as your main light and use the other bulbs for secondary side lights to light up the lower branches unless you don't have the room to accommodate them. You should see quicker results with the hps alone or in combination with those 125w cfl's