It's difficult to name one "best". It's much more objective to list "TOP TIER".
TOP TIER companies I have encountered over the last three decades.
Valve Amplication Company - Do not be surprised if Kevin Hays answers the phone himself. He is the quintesential gentleman as has been stated many times on this forum. Fantastic products.
Linear Tube Audio - Nicholas is quick to respond and has the right answers. LTA makes some very nice products.
Audio Advisor - Good to very good products. Very quick response time.
Quicksilver Audio - Mike Sanders makes great products, responds on a timely basis to questions. Even my stupid ones.
Mapleshade - Eldon has great products and is very responsive. He spends an abundant amount of time making sure he understands exactly what products will work best for you and makes great recommendations.
Oliver Sayes - if you want a custom amp or pre amp Oliver is a great guy to work with.
Abbas Audio - Abbas makes great tubed DAC's. He has some other products as well. He responds to questions. Being a very small outfit, I don't understand how he does all that he does.
Spatial Audio - Great speakers and great service.
If you buy something new be sure to check the warranty terms and conditions closely before you buy. There are several good reasons to buy American even though some of my gear is not. If you don't buy Anerican check that they have service available in the US (if you live in US of course) or be prepared to pay serious shipping costs and endure the risks involved in shipping.
If you buy used, be sure you know where you can get repairs done for that item. Most of the good repair shops are backed up for months at this time.
I'm not ready to hammer anyone at the moment butI I have a situation in the works that is not up to par.
ENJOY THE MUSIC