My friend has the 237 paired with JBL's.
Sounds great, rich deep bass and very good
I have the Vincent SV-500 and like it very much. Coming up on 3 years of ownership. The Amp is connected to Martin Logan Motion 40's.
I originally wanted the SV-237 but at the time could not justify the extra cost. But I am fine with that decision now. I never tried to upgrade the tubes simply because as is, my system sounds great to me and I did not want to take the risk of losing the sound that I have now.
I can't really tell you my experience as some big audiophile with audiophile terminology. All I can say is that it is quite satisfying to listen to but of course, speakers also matter very much. I do not feel that my system sounds cold or harsh (regardless of the content that I am listening to). Everything sounds warm, inviting and rich.
I hope that helps a little.
If you have any questions, please ask, I will try my best to answer them.