IMO...FWIW
Find your online tire deal and determine full pricing. Call a national tire chain and ask about mount balance. In my experience, they'll try to meet or beat the price you're getting. Many of the big boy tire chains have salesman working on commission, so they're going to be interested in making a deal. Complete the full transaction with them (including road hazard warranty) and then you'll have nationwide service in the event of a failure. If you buy online and have your local "mom and pop" tire shop mount/balance, then that's where your warranty is (if any at all). For as much as I drive/tow/haul, I like the idea of having road hazard warranty recognized by a national chain. This is one of the exceptions I use when deciding whether or not to buy from small and local businesses.