Not assure what you mean when you say, "...carver didn't match the mono blocks when the were shipped." I have totally different tubes in, than the tubes that came with the amps. My Cherries appear to be matched when I have all the new tubes in and bias each amp with one another. Again, I'm not sure if this is the "matched" you are speaking about. Please elaborate.
When the tech spoke of biasing in the 140+ range, I think that was pertaining to the KT-88's being used in the Cherry 180's and not the KT-120's. I believe the KT-120's can be driven fairly hard and not be worn so easily, but I could be wrong.
Not sure why your bookshelf speakers would cause the meters to "peg" more than your floor-standing speakers other than the bookshelf speakers being far less in their efficiency rating. My speakers aren't too efficient and are power hungry, so I think that's why mine "peg" hard at high volumes.
Not sure what city-state you are in to recommend a tech. there, but I'm in Compton, CA. Yes, THE Compton lol Anyhow, I have had my tech in Westminster, CA, (a really nice part of town) rebuild my x-over network in my Infinity IRS Beta mids/highs towers; fix a troublesome woofer in my Thiel CS5i speaker; along with several other amp and transport/DAC work. I'm sure he could handle the attenuator and/or the V-cap upgrade. I am not sure if you can do PM's on this forum, but here is my email address dblf@pacbell.net
Hit me and I'll shoot you his info. and you can talk with him directly and get a feel for him. He was recommended to me by a Volleyball dad on my daughter's volleyball team about a year or so ago.