I second Costco. The Price includes free rotation, warranty, mounting and balancing. No hidden fees and when I bought my KM2's, BFG was giving a $60 certificate if you buy 4 tires. The price and service a lone is worth the membership or you can do what I did which is legal.
Anyone can sponsor one person on their account. This can be a wife, Family member or a friend. My friend added me at no cost to him or me and then I proceeded to buy my tires. The guy at the Tire center told me to do this so I can receive the warranty under my name. They even went as far as mounting the tires while I got added to his membership.
I was totally against joining any store that requires me to pay a membership to buy their stuff but after seeing the customer service, Gas prices they have, and warranty on any item... well ....I think I am hooked in buying a membership on my own and then sponsoring my wife.
The guys at every Costco tire center have been great and helpful and the total out the door price was still cheaper than Discount which I have been going to for over 15 years with no complaints.
Cheers,