ADCOM

I owned a GFA-555 for 30+ years.
I worked as good for all those years until I sold it a year ago.
Nelson Pass did a great job on those amps.
I have no experience with other Adcom equipment, but suspect it to be equally good.
Bob

I own a 545v2, also a Nelson Pass.. sounds pretty good.. especially for about $250.. I keep as a back up for when my main amp is being switched or fixed.. I never feel I'm missing that much when in use.. My main amps float n the $6000- $8000 range new

Gfp750 preamp and gfa565 mono power amp.

I've owned various Adcom items and they were always nice sounding and reliable...I went for the tuner-preamp with a 535 when they first came out, later a balanced preamp (can't remember which one) used with different power amps, and more 535s (used and new, including the 535II) both for studio and otherwise. Sold 'em all eventually except a 5300 that's used for remote (deck) speaker duties...that amp sounds great and was seriously inexpensive used. Nice stuff, but watch for oldness issues...leaking caps, hair loss...