Find a Modwright SWL 9.0 sig ($1200-1500 used). This is a tubed linestage preamp and it will make your Adcom sound very sweet indeed. I used one on my Adcom GFA 555 and I was very impressed. The pre amp is a KEY component, keep your amp and do it a favor by adding a proper preamp. The Adcom preamps do not sound good.
Matt M
Matt M