No one is buying "more expensive" stuff because they can't tell the difference, that is the last reason you would get something expensive. Generally on this planet, however, the things that sound better also tend to cost more. It's easy really.. do so some research, narrow down the things you might like and can afford, go to a store or a show/meet and have a listen, compare it with some other stuff, if you love it, buy it, and be happy. Doesn't matter what anyone else does, says, or thinks. Be warned though, when you go to the store and ask to listen to setup "XYZ" and he says let me set it up for you while you listen to this Liquid Gold setup I have here, say thanks but no thanks, take a seat and wait. Because it is a trap!
Loosen up a bit, splash some cash, you only live once, there is some great sounding gear out there!
BTW.. double the frequency ensures perfect reproduction only in theory, if you can sample with exact precision, which doesn't happen with 16/24 bits in which case a higher sampling rate may in fact be better.. but if you can't hear it in an ABX test then it didn't happen.
I agree with the buying stuff principle u talk about....well spoken!