I had an MX110 for a while but never had any tube ARC preamps. I rebuilt the MX110 completely and it sounded a lot more modern afterwards. Beforehand, it was soft and was lacking top end extension. Afterwards, it was surprisingly good. I wasn't expecting to hear a sort of "hifi" sound with excellent detail and transient snap - not exactly "tube-euphonic.". But I wouldn't advise you getting an MX110 (or original C22) without an overhaul - they are 40 years old these days.
Arthur
Arthur