@treepmeyer +1
Its hard to know which brands are truly successful without seeing financials. I would start with brands that have stood the test of time without bottoming out financially or selling to big corporate, which often results in the brand continuing in name only.
Accuphase, Pass Labs, and Grado Labs come to mind. Burmester, T+A, and Zellaton are German brands that qualify. Audio Note, Kuzma, Air Tight are other examples and there are many more. One common thread is that all these manufacturers have been known for many years-decades-for building high quality, reliable stuff. As far as I know, they've not succumbed to the temptation of VC buyouts. Each of these companies have a loyal following and concentrate on their core business. They must be doing something right.