You kinda have to go out and hear some of the candidate amps. Tube amps vary in sound MUCH more than do solid state amps. I am a tube amp fan, but, I find that a lot of high powered tube amps sound brittle and unpleasant on the top end. This has been the case with some, but not all Audio Research amps, so at the fery least, listen to some tube amps. Also, consider not going the high powered route; a lot of people starting out with high powered tube amps amps end up buying more modest 40 or lower watt per channel tube amp.
You have a nice linestage so I know you are looking for a power amp, but, you should listen to something like the Synthesis Audio A100 tube integrated amp (it has a very good built in DAC too). The company makes power amps too, but they might be a bit high in price. My local dealer has a lot of customers switching to A100’s (100 watts per channel) or its baby brother the A40 from some pretty exotic solid state amps (e.g., D’Agostino, Pass Labs) and tube amps (e.g., top end Jadis).