Once you hit the upper echelons of performance, "better sound" becomes even more subjective than otherwise. IT comes down even more to personal preference to determine what is best. Build quality is another issue and is probably less subjective, but alone build quality does not necessarily mean "better sound". The best products tend to be built by the smartest and most capable designers who will choose the parts needed to meet their goals. Depending on the target market, they may decide to always use the best most expensive components or those that may cost less but meet the requirements of the design just as well as the more expensive parts. Quality control and assurance is always key no matter what. That is really what separates good products from the pack, especially when one is paying a premium for a supposedly "superior" product.
