I must confess that I get bored with my main system if I don't change it. There's nothing wrong with the sound...in fact, it's the best sound I've had in over 50 years. But for me, the fun is in changing things up and seeing what happens. When you make changes that after a while you realize might a step back, well, that is the time when things might better be left alone. Case in point, I acquired another identical amp and ran them in bridged mono. While some things changed for the better, it took me a while to realize that the sound from the stereo amp was purer and more musical. The second amp is now gone. In its place, I acquired a second phono preamp I did not really need. I am playing around and tweaking this. It might not be an upgrade in terms of absolute terms of sound quality but it has kept me more engaged in listening to my system. That's what it's all about for me.