Use pink noise disc to warm up stereo

While I can't speak to your stereo, my experience is that it just needs to be on to warm up. Pink noise, though, is allegedly good for breaking in signal cables, where a signal needs to be passing through the cables. 

I'd be interested if you notice a difference between warm up with no noise and warm up with pink noise..

Hmmm. Odd. I find just being turned on for a bit does the job. Which is odd, as I have a similar setup to rvp: dared tube pre and Ghent Audio class D monoblocks

Do not keep tube amps on all the time. That's a fire waiting to happen.