I disagree with the above post. Heaters and pumps aside, your tank water is only heated when it's directly below your lights. Therefore, if you add 650 gallons and hook it up remotely, it would take more time for your lights to heat up a larger volume of your water. (Plus while the water travels away from your lights, it would have some time to cool down a bit provided you're not holding the temperature high w/ a heater)
I would however, still keep the lid partially open. Even though it will take more effort to warm your water, you still want it to cool off somehow.