I've had Klipsh KLF-20 (and KLF-C7, KSP6) for over 20 years. Mine is not modified.
I've tried a few different amps (NAD, Rotel, Nakamichi, Plinius), and AV receivers (Yamaha RXV-3000, retail $2000 and Denon AVR 3803CI, retail $1600) for KLF-20, and to my ears, not much difference. My KLF-20 sounds just good.
However, I've had a few different speakers (Tyler Taylo, Tyler Linbrook, Apogee Diva, Harbeth C7-ES) and they all sound better than KLF-20 on stereo music (especially on classical and jazz). Though for Rock and heavy metal, KLF-20 sounds more live, but I don't listen to them often.
So, I use KLF-20 in my home theater setup with Denon, and other speakers in 2 channel stereo.
My 2 cents.