Is it worth selling the original 18 volt tools and upgrading to the new 20 volt line ? Mine ll all in great shape but the batteries are all shot. Is there a 20 volt max cut off tool like the DC410? I would not even be considering the new lithium ion 20 volt max line if a carpenter friend of mien did not show up to help me build a new bar with his new Makita Lithium ion drill driver set up ! super light powerful ( and with a nice led light)