I think it's interesting to listen to an amp or other component as it breaks in...unless it sucks so bad before break in you can't take it (recently had some balanced cables with precisely that issue...they were banned forever from my system in one day). My Silverline speakers took a while to develop their mojo, as did my Kavent preamp...both eventually found their way, and I'm glad.
Amp burn-in..Best technique
I will soon be getting my new Mcintosh MC591's. I am curious,......does it matter how loud you play? If I run a CD on continuous repeat,...does it matter if I turn it way down? Or does that not offer enough resistance/load to drive to have a "break-in" effect. My wife would not be happy if I had my system playing at high levels all day.