OK I say this every time, we are a manufacturer of tube components and we are a repair/upgrade facility. You actually do not know how a component will perform until you try something in your own system.
In our listening room we have a pair of Sonus Farber Stradivari speakers. We typically use our tube mono blocks on them at around 35wpc. We have used many other mono block amps since we repair components and get to try them out on that system. Recently we received a VAC Ren 30/30 stock stereo amp. That little sucker worked fantastic on those speakers. So, you don't know until you hear it in your own system.
If you are looking for warmth, I would say that the AR is not a champ in that area. Maybe better than the Krell, but I don't know what you exactly mean by warmth to your ears. The old Krell KSA-50 was a fantastic power amplifier back in the day so it depends on different models what floats ones boat. I would also say that the PS Audio DAC is not a typical warm sounding piece either.
Happy Listening.