Mike - I still use an Adcom GFA5400 in my wood shop but before it was in my shop I used it in my home, as you mentioned the sound is powerful but slightly grainy. The 5400 was replaced by an Anthem PVA2 and I noticed deeper, more defined bass and a much smoother sound.
The Anthem amp is just sitting in my closet unused since moving to an all AVA system. PM me if interested.
Changing amps will be more subtle than changing speakers, but the Adcom will impart it's signature on new speakers too. A sub could be an interesting solution. I used to have one of those Dayton $100 subs, it was OK for a home theater but lumpy and ill-defined with music so I sold it to a friend who is deaf in one ear for his home theater.
Wayne