I'm not a fan of Parasound.
Have you considered having the Adcom rebuilt and upgraded? The two techs that I'm familiar with who upgrade the GFA-555 are John Hillig at Musical Concepts and Chris Hoppe at Hoppe's Brain. Both are well respected and get great reviews/feedback.
Might be nice to keep the Adcom for nostalgia's sake, especially if the upgrades offer significant improvements in sound quality.