^^^Read that thingy^^^
A relay is a good idea even if you get a switch to handle that kind of power because for one all that power is now inside where you are at (bad cause harm will probably come to you or any of your electronic equipment if it fails) With a low power switch and a little 22awg wire your not gonna harm anything. Plus with a relay there is less resistance (not that there is that much anyways.) and a shorter path for the power to go directly to the lights instead of into the cab through a switch and all the way back out into the lights.
I run relays on all my lights, I even did the relay set up for my regular headlights and there is such a difference! Not to mention with a relay and a switch you can keep the switch on and have the lights come on when you flip on your highs.