Im sure your thinking of this issue much like putting indoor raised plants outside in the sun,am i correct ?
If so no worries there,what hurts indoor plants when they are placed outdoors in the sun is not lumen intensity but uv light,indoor plants are not used to getting uv light rays & when they are thrust into recieving uv light it hurts the plant,this is not the case with extra HID lumens.
When you switch to the big light your plants will pop a boner & i dont mean hermie either,think of it like the girls nip's getting errect

,they'll love the big light & show you how much they love it in a few days.
I stated out with multiple 400 watters much like you,i saw a huge difference once i inserted a 1,000 watt hps into the mix,now i only use 1,000 watters for the bulk of the lighting & 600 watters for side lighting,the 400's are relegated to emrgency lighting should a ballast go.