You can just reduce the wattage of each lamp. If you have 150w lamps maybe change them to 90w, etc... Another possiblility is to get a dimmer for them and you will still be able to turn them up if you need the extra light. If you go with the dimmer you need to calculate your total wattage and go with a dimmer rated for that wattage or higher and it must be able to handle "par" lamps, it will say it on the packaging. The last option that comes to mind is to add a switch or two so they dont come on together but that is the most expensive and complex option.