Personally, I prefer to go w/ authorized sources. I bought a my plasma, HD Tivo, and Pioneer Elite 45TX all from authorized sources. W/ the exception of Tivo (Magnolia), they were online purchases. I bought an extended warranty on my HD Tivo because Magnolia is local and I can have them deal w/ exchanges. I also have a local Panasonic service center for my plasma and I've already had a warranty replacement that wasn't too bad of an experience.
3rd party warranties can be a hassle when having to deal w/ fine print. Case in point, I have an extended warranty on my BMW 528 wagon. Twice I've had it in for repairs that normally would've been under a standard warranty, but the warranty house uses loopholes in order to cover only 25% of what they should. I would've been better off saving the money on the warranty.
Who knows, you might not ever have to use the warranty, but if you do, be aware of the problems that might occur and whether you're willing to deal w/ them.
