It seems like your choice then is to go to a dealer and pay the markup for full service. That has its own set of problems, for example you will only hear what he sells, not necessarily the best, or the best value.
I too would be interested in a comparison that isn't going to happen: What's the difference between my ten year old FET Valve preamp and the current Ultra and Insight models and the new differential ones? Oh, it's a SL so it can't be upgraded to the latest Ultra... I'm happy with what I have, so I'm not in the market, but if I were, that would be my situation to resolve.
I've resigned myself to treating this hobby like buying a car. If I don't need something, it's best not to look, lest I create dissatisfaction with what is already good enough. If I need something new, only look in my price range. Do some research, but view the researchers with a bit of skepticism. They might be honest and objective, but they might not be married to a five foot tall lady who will also drive what I buy. (Their speakers are not my speakers. Their room is not my room. Their music is not my music.)When I find a good brand that delivers reliability and value, I need a strong reason before looking elsewhere. I resign myself to the fact that I will always want a Ferrari, can't afford one, and would very likely be unhappy with it if I had it. Consider used, with caution, where it is appropriate. Some people sell perfectly good things at a loss, because they want something new and different. Other times, there is a reason it's for sale, cheap.