I have a Musical Concepts modified Adcom 555 John did for me back in 1989. After reading the review in Absolute Sound ( Volume 13,Issue 55,1998)by Frank Kaplan I pulled the trigger and sent it in for mods. Unlike the one in the review I had mine turned into Dual Mono with Dupont Teflon caps and the Platium mods plus Edison Price copper binding posts. It came back sounding like a warm tube amp,gone was the edgy highs and the bass was tighter and more controlled. This amp has driven Vandersteen Signature 3's,Infinity RS3B's and Odyssey Lorelei's with no problem. I still have it and pull it out every once in a while and fire it up. I used it with the Adcom 750 pre amp that Musical Concepts modified to platinum level and it sounds very open,extended an imaging is dead on.
I doubt you would be disappointed in the money spent vs. results.
Yes I moved on to a pair of Plinius 100's mark 3 in mono mode but the Adcom has a sweet spot in my heart even today.