New Preamp Suggestion

Well Mike, then I would suggest he consider a preamp from VAC, ARC or Aesthetix. My choice would be to look for a used VAC Renaissance mk III, as I think that would provide the best sense of air around vocals and instruments. Very dimensional

I have also owned a ARC Ref 3, and that was a fine preamp too, so I'm sure he'd be happy with a Ref 5 SE also. The ARC may have a slight edge in bass control over the VAC. Although I haven't owned a Aesthetix Callisto Signature, I have heard one, and I would put it in the mix with VAC and ARC as far as creating a deep, detailed musical stage.

The BAT CJ and Cary models will tend to sound warmer and a bit more musical, but won't have the air and detail in the high's of the VAC, ARC and Aesthetix. The BAT probably has the most powerful bass, though I would not say it has the tightest bass control.

As always, YMMV.

Just be careful when adding a tube preamp. Or even another solid state preamp from a different manufacturer. You don't wanna have impedance mismatching.

An Emotive Audio Epifania with Duelund CAST output capacitor would be really nice.

@Dave_72, his friends Classe CA-M600 amps have an input impedence of 50K ohms, so he should be safe with just about any preamp.