I can understand the liability about not wanting to plug a tire, but I wouldn't really want a patched tire on my 150 mph sportscar either.
Most of the "quality" tire shops or dealers should have the newer higher quality tire machines meant to work on large wheels w/ low profile tires. As for "Pep Boys" we don't have one in our area. But looking at the company, I would compare it to buying a Big Screen or High dollar Nikon camera at Best Buy or Wal-Mart instead of a localy owned high end Home Theater store or Camera shop.
Sometimes it will cost you WAY MORE in the long run to save some money. Customer service isn't that hard to find, unfortunately you do have to pay for it. I like being able to walk in and have someone who knows my name, if I have a problem, they take care of me. I will pay a little extra to know I'm going to be taken care of. Other than a dealership, I'll be taking my Corvette or dad's SRT-6 to a local tire store thats been in business for over 30 years.
But we do have a Sam's Club....Maybe they'll be running a sale.