901 series 2 speakers

Since you are retired and wanting to keep you 901 Series II, I would suggest recapping your equalizer if you haven't done so already.  Also, I have found my Series II to work better with an older receiver vs modern separates.  And since you have owned them for over 40 years, you probably know that they should be placed according to the owner's manual, I.e. Best on the tulip stands, so many inches from side and rear walks, and not to place any objects in between.  I did all that and the bass was incredible.  I was hearing deep rumble on tracks that I never heard on another system.  I did miss the highs of modern silk dome tweeters.  Good luck.