@djb, I agree: preamps can make a big difference, especially if you venture from solid state to tubes. I had several of both, but the biggest differences are between the tube components, (IMHO). My personal approach is to employ ultra-low distortion up & downstream components, and use the preamp to add color if you want any.
Don't be put off by the standard "level matching" and "blind ABX" testing comments. It's the norm around here and, I suppose, the justification for the "science" part of ASR. Fine, but this would be a dull place if every personal impression had to be thus proven. Ultimately hi-fi enjoyment is about your own subjective enjoyment, not about "proving" your impressions to skeptics.
Don't be put off by the standard "level matching" and "blind ABX" testing comments. It's the norm around here and, I suppose, the justification for the "science" part of ASR. Fine, but this would be a dull place if every personal impression had to be thus proven. Ultimately hi-fi enjoyment is about your own subjective enjoyment, not about "proving" your impressions to skeptics.