Should Amps be plugged into a power conditioner?

Definitely directly into the wall… and preferably into a dedicated direct line. Perhaps some very unusual  amp / terrible power situation it would be better… but I have not experienced it or heard of it. 
 

My dealer recently brought over a conditioner specifically designed for just the amp. I wish I remembered the name… it was high end, you’d recognize the name. The audition lasted about a minute… although I spent more time with it. Definitely restricted dynamics. 

@bigboypete 

Congratulations.
 

remember when I did exactly as you. Same result.

Then I put in a direct line and an even bigger improvement.