As good as it gets

good notes on amps should be sounding nice out of box and break-in only slightly makes it better. 

Yes but that is the answer to the question of I don't like this but they tell me it just needs to burn in, is that true? And the answer in that case is: no.
But that's not the question here now, is it?

The first question the OP asked has been answered. The second question he needs to do some homework and resubmit.

My all tube integrated amp took some time to sound it's best, whether its the internal components or tubes I can't say. Then I could begin tweaking my system for better performance. I sounds wonderful now.

After I spend some time listening to my HT system I'm always amazed and impressed when I fire up my 2 channel system for some vinyl or cd playback... even FM radio is a joy to listen to.

Tubes can take 2-300 hours to fully settle in as well as coupling capacitor 
50 hours not possible 

Don't forget the brain. It also has a 'burn in period' when using new gear.