[quick]

@ 65K miles, regardless of what and where you buy, it's not going to be cheap, period.

Warranty companies look at few things that helps them price the car
Year: The older especially past 5 years, gets expensive
Still under manufacturer warranty? (best time to buy one is, few months prior to your original warranty expiration)
Miles: < 30, < 40, < 50, 50-75, 75-100 and above 100. The higher the more expensive.
Modifications: Make sure they cover the mods
Exclusionary vs Inclusionary: Always get an exclusionary where they tell you what's not included
Miles driven: If it's a weekend car, make sure they know that too
Garaged: Discount for garaged vehicles
Price: Never buy the cheapest or on price alone. There's a reason why 3 companies are close enough and the fourth one is $1500 cheaper.
Best extended W company is the one who your local dealer recommends or better yet, ask them about the one you are interested in