...walk....walk....trip...bang...boom....what the.....who put this soapbox here?
It's funny every year how we "just made a new break through". Is funny in the scientific community how year after year someone thinks they have beaten the laws of physics...only to find out they just made a good break through in efficiency. Sometimes not even that.
When it comes to amps you will generally find that the more money you pay the better amp you will have. Why else do you think that amps from the same manufacture cost a price range that can be a spread of 800% in price difference. It's not like they cost much more money to make. They just know that they will sell less of the higher end models because they will fail less so they have to jack up the price. Wana know how far behind amp technology is then look at the inputs and find an amp that has a Digital input. Not that many out there.
Knowing what amps work is knowing how amps stack up "real world" wise against each other. Sticking to what you know and a little bit of luck that the manufacture hasn't changed the manufacturing process on you.