I am going to be doing a complete gear/axle upgrade on my rig as soon as ARB D44 rear lockers are back in stock. As part of the upgrade I want to put better than factory rotors and brake pads (the rears need to be done in any event). My shop said they would do the install for free. Is there a really good lower cost upgrade (like < $400) to upgrade the rotors and pads?

 

I would say the Teraflex Big Brake kit, but I think that exceeds your spending limit. Anything cross-drilled and slotted will help reduce heat build-up. They aren't that much more than OEM replacements either.