Extended warranties are a gambler's proposition. True, most receivers are quite reliable and, not abused, will last much longer than a couple years, but, here and there, there are a few bad ones. It's safe to assume that the cost of one repair is greater than the cost of the warranty. So, you are gambling that the receiver will blow up before you are finished with it and so you buy the warranty. The company, on the other hand, is gambling that the receiver will outlive the warranty.
The problem is, that the company is playing with a stacked deck. They know what percentage of units will fail and how much they cost to fix and they price the warranty so they don't lose on it. I've had a lot of components over the years, never bought a warranty and the only ones I have lost were due to an "act of God" (a lightning strike, covered by insurance), so, if at this point, my new HT receiver burns up prematurely, over the long haul, I am still ahead, having not paid for extra warranties.