Like so many others here, I've owned numerous truly great bass amps over the years.
The first amp I ever owned was a 70s Ampeg V4B that I picked up used for $200 back in 1987 at age 19. I was too inexperienced to appreciate what I had and was talked into selling it and buying a brand new solid state bass amp that was low on power, low on features, and sounded terrible. My bandmates convinced me that it was better to have a brand new, reliable, solid state amp, than an old, unreliable tube amp.
In the early 00s, I picked up a used Mesa M2000. It's not a well known amp and they weren't very popular, but I fell in love with it because its (ridiculously) extensive tone shaping capabilities allowed you to get just about any kind of tone out of it that you could imagine. It was particularly suited to an aggressive, growly, grindy, midrangey tone that I was playing at the time.
To me, that amp was a near perfect combination of vintage and modern, with a multi tube preamp section and MOSFET power section. It sounded glorious running through a TL-606 cabinet.
Much more recently, I stumbled across a great deal on an Ampeg SVT-4 Pro. It had more power and more features than I could ever hope to use, and it sounded like
The Voice Of God. It would shake concrete buildings while turned up only halfway.
But it was big and heavy, and was completely overkill for the 3 piece rock band I was in that played mostly small, local bars, so I sold it.
Just two years ago, I decided that I wanted all the benefits of a modern, compact and lightweight, Class D amp, so I retired the M2000 to home studio/recording use and bought a Mesa Subway D-350.
After gigging with it for two years, I consider it to be the best amp - at least for me for gigging purposes. I believe it's as close to perfection as I'm likely to see in what remains of my bass playing days.
I just set everything flat and it automatically pumps out great bass tone that sits perfectly in my band's sound mix, without any need for modification by the FOH tech.
The Mesa Subway series of bass amps seems to be the industry leader among today's working bassists, and to my ears, that status is deserved.
