I moved from a 25 year old Adcom 545 II to a used Parasound 2125, and could not be happier. I can't even get the thing to clip with my KEF Q85s!
At the same time, I bought a Zpre2 on a whim, which went unused for the most part. One day, I started swapping around 2ch gear and installed the Parasound pre, wow....quite surprised how much more clarity it had over my NAD T168.
So, I dumped the NAD for a Parasound 7100, again, wow....it's so revealing and clear. Did not expect a performance bump, but it's clear as day. My main system is 2ch, even when I had the NAD AVR, so I really didn't care if I bought a full-sized 2ch pre amp or an AV pre, but the Parasound preamps go for over $600, the AV pre cost less than half of that. Either way, my amp and preamp brand is Parasound, for good.