Tubes (EL34) + room treatment (if too lively or have any slap echo, and at least treat first reflection points) + Cardas Cross/ Golden Cross cables + baffle edge anti-diffraction device (as sold by Jim Goulding) + CD treatment (such as Le Art du Son) + speaker toe-in adjustment (so not pointing so directly at you) + subwoofers (at least two, unless your mains already go to 20-25Hz on their own) + dangle a paper towel over your tweeters.
I've tried all of these things. They all had some kind of positive effects for playing those crappy CDs, but some of them detracted from the quality sound of good CDs, so I now only listen to those crappy CDs from another room or in my truck.