Preamp Opinion

A couple of weeks ago, I asked for advice on my amp and preamp. Although I am sure that it could be improved, I have come to the conclusion that the Parasound A23 is the least of my problems. I also have a Parasound New Classic 2100 preamp, a Marantz 8600 CD player/streamer (which I also think doesn't need to be replaced), and Focal Aria 926 speakers. I did listen to advice I was given and am expecting a vintage McIntosh SL-1 sub to my system.

I am looking at a few used preamps and wanted to get your opinions on them since the only one I have heard is the Adcom GFP-750 and that was years ago. My memory is that it had a very good sound to it. The other preamps I am considering are the Rotel RC-1572, Rogue RP-1, Coplant CTA 301 MKII, Bryston BP6, and Vincent SA-T7. Unfortunately, I have not heard any of them and don't have a location where I can. I tend to prefer a sound that is not too bright but provides a good clear soundstage and imaging. I have always owned solid state before and am a little leery of tube maintenance.

Thank you for your advice or observations about any of these preamps.