the sound of the "new" amp is decent with my turntable, and terrible with my CD player.
My guess would be that's because analog is so much better than digital. It may not be your CD player, but your CDs. Or both.
When I upgraded my speakers, I could no longer listen to CDs, because (I thought) the CD player was not as good as the rest of my components. I could not listen to ANY CDs without cringing. My records sounded even better though.
Then I upgraded my CD player, and sure enough, many of my CDs sounded much better. But the MAJORITY of my CDs still sounded awful, many of them even worse, and those I just ended up giving to Goodwill. Many of these were from the 80s and 90s, when digital recording and mastering (DDD, "all digital") was considered the apotheosis of recorded sound.
The (sequential) upgrades of my amp, speakers, and CD player gave me some wonderful sound, but also limited me in what I can listen to. Crappy recordings and/or masterings just do not cut the mustard any more. I have to be more diligent and discerning in what recorded material I choose to invest in (both digital and analog, but especially digital). It's a bit of a trade-off, but one I'm content to make, because of the wonderful sound I get with the right recordings.