fyi, The Adcom GFA 555 II is very good high current amp from the 90’s. I have a GFA 585 and a GFA 5503 for my home theater setup. I am the original owner of both of them. They have been in service since new. The caps went bad on the GFA 585 and the GFA 5503 also had to be serviced about 10 years ago. For me, the sound of your 555 II will directly correlate to the condition of the vintage caps inside. If your GFA 555 II is running to spec, then, it will be hard to hear a difference with a similar rated amp at modest volume. If it is not running to spec, it will be easy to beat with almost any decent running amp.
