I experienced a radical sonic change when I auditioned a Mesa Baron (amp) in place of my much smaller Cary SLA 70 (amp). The sonic change was not entirely positive, so I stayed with the Cary.
Later I did pick up a pair of ARC VTM120s (amps) and the sound was a lot like the Cary (both 6550 based) but there was much more sound, and I do not mean much louder. (I don’t have the ARCs anymore as I made a somewhat lateral move for a cary that was larger than my first Cary and more reliable than the ARCs..)
The amps in all of those applications were important to the listening pleasure I was experiencing.
Going back to the first three amps I mentioned (Cary, Mesa, ARCs) I ran them with a B&K digital HT preamp to begin with. In ’99 I paired the great sounding but unreliable ARCs with a Cary SLP90 (12au7 tubed preamp) and the transformation was remarkable. warmer and sweeter (for those that like that) and just way more musical and engaging sounding. A couple or three years ago I replaced (although I still own it) the SLP90 with a Cary SLP05 (6sn7 based preamp) and there was another remarkable transformation. Wider and higher sound with more air and detail but not as warm and sweet.
So based on my relatively limited experiences, I see them both as important to ultimately enjoying the sonic experience, but I suppose that if I had to get one or the other right first, I’d say to start with the preamp. Although that is opposite of the way that I went.
But good question, and not an easy one to answer with a one size fits all reply. In my opinion, anyway.
