My choice would be the venerable Stewart/Bowser/Kato F unit chassis. If you find one wothout the 8 pin socket that is easy to remedy.
I have a bunch of Proto, Athearn, Intermountain and Broadway F units and, although they are “usually” mechanically sound with good motors there are often noises or pick-up issues that creep in.
I’ve probably had three-dozen or so of the Bowser-type and, other that a few bad motors in one short period, they have consistently been excellent and smooth running chassis.
When evaluating speakers, BTW, keep in mind the great effect the shell has with providing a baffle and amplification of the sound. I always evaluate speakers before, during and after a DCC sound upgrade.