Another thing about buying your Mac from any third party (like Best Buy or anyone else) - check to make sure this is not a previously returned item. If it is not new, Apple will likely not consider your purchase date as the "start of the warranty" but use the purchase date when it was really first purchased. You can always contact Apple and ask them if the serial number of the unit you are considering buying is really new or if it has been purchased previously.
Be careful - it happened to me and I lost 9 months of the warranty since it had been first purchased long before I did it at Best Buy.
Third party companies may not tell you this and pretend they didn't know about this but they certainly should.