Warm up - yes, both my 370 and 380 power amps need 15-30 minutes to fully strut their stuff.
It's worth the wait, though.

Try it with the 270 pre, John - there is real synergy there. We prioritise very different music, but it might work for you, too.  It gives a fuller tonality with more rounded and present 3D imaging, even the speed and precision of transients is enhanced.
Functionally, my system doesn't need the pre for 98% of my listening, but I still prefer it in the system with my 380 for its sonic benefits!