I think that the issue is the usual faulty thinking of chances. Your Denon failed due to age. Your Sony was a failure and your chances of having a dud is the same as everybody else. So I highly doubt you have a power problem. Those issues are very rare and you have eliminated as that as the cause already.
Its like flood ratings. We build in the US to 100 year event ratings. That means the chance of a flood in 1% per year every year. If you flood it is still 1% ext year and the year after that. So there is a 1 in 5 chance you could flood every 20 years. So building on a 100 year flood plan is dangerous. We should build to 500 year events.
Receivers are a problem, with far too many features at too low a price. They are fragile, not robust, and prone to failure. They are essentially troublesome units. Personally if I bought a receiver I would expect it to fail before I had any lengthy use from it. I really do buy for the long term with an eye to reliability. Having said that judging reliability is the most difficult aspect of any purchase.
But I try, and have a lot of gear in regular use that is very old.
In the wake of this crisis and how the world's monetary system will radically change , I suspect most of this Far Eastern junk will disappear from the market. We will return to the kind of quality that was around pre 1970s when the rot really started to set in.
