Surely the best approach will be to stick with those companies that are tried and tested, the usual suspects, and those left-field candidates that have a solid provenance like NAT Audio. How many companies on your friend’s Mono And Stereo website are still in business 12 months later?
I think that geographic location and distribution is a key point in this search. Many of these small companies have excellent products, give good local assistance and service, but are not able to give worldwide assistance.
Playing the devil's advocate, IMHO NAT Audio ranks with the other usual suspects ...