I found your findings on your KLF-20's quite interesting and a little familiar to my own experience. I have both the KLF-30's and KLF-20's and I also run Emotiva amps through them. If you are listening mainly to Pink Floyd, The Police and Dire Straits and you find the KLF lacking bass or dynamics, I would look to your Kenwood Preamp as the weak spot in your system. I had to look outside the box before I believed it for myself.
I used a vintage Technics preamp initially with my Emotiva XPA-2 I have to admit, I was not overly impressed with the results. Even on Heresys the sound was kind of dull, which surprised me because the Heresys are known for their detail and punch. After about six months I decided to move to an Emotiva XDA-2, and right away I heard improvement in the overall sound ...however the dynamics were still sort of lacking. I found the bass to sound a bit dull, lifeless and even a bit muddy. Whether I was listening through my Infinity SM152, my KLF-30 or my Heresy the sound was good, but not great. It sounded like something was lacking.
I had been extremely happy with my Sherbourn SR-120 AVR that I first bought new in 2013 from Emotiva when Sherbourn and Emotiva merged. The Twin Cirrus DAC chip in this AVR sounds fantastic, I would even go as far as saying it rivals my buddy's audiophile $3k Bryston Preamp. I now own four of these SR-120, I enjoyed the sound that much. After a little research I found that Sherbourn also made Pre/Pros with a similar if not identical chassis and set up of the SR-120, minus the amp section....the PT-7020C4 is one of them.
So I sought out the Sherbourn PT-7020C4 Preamp/Processor to find out if this preamp could give me that same distinct sound and detail as I got out of the SR-120 to pair with my Emotiva amps. At first I paired it with my XPA-2 and XPA-5 for home theater, and once again I was extremely happy with the dynamic response, detail and clarity the pre/pro was putting out.
I wondered since I enjoyed this sound so much, how would it work in a two channel set up? So I decided to try my Sherbourn PT-7020C4 with my Emotiva ERC-3 CD player hooked up with my Emotiva XPA-2. I went from the ERC-3 into the balanced analog inputs on the PT-7020C4 and out to my Emotiva XPA-2. Once it was set up I ran it with no subs, no EQ, no ARC and could finally say everything came together for me.
I am absolutely thrilled with the outcome. The Twin Cirrus chips they used in these Sherbourn is nothing short of amazing. It breathed new life into my speakers in two channel and pushed the KLF into phenom territory. No mods, no bracing, no re-glue. ( I was lucky enough to come across three mint pair of KLF-30 and I have not dared touch anything.)
I now run all four of my two channel set ups with this PT-7020C4, plus I have two more pulling home theater duty. Along with the four SR-120 AVR's I couldn't be happier.
Before you give up on your KLF-20's you owe it to yourself to try a different preamp. I found the bass tightened up, the mids and tweeters are still strong but more natural sounding (before I found the vocals, especially female vocals sounded a bit nasal. It was pretty noticeable through the Technics preamp and less so with the Emotiva XDA-2. That all ended when I hooked up the Sherbourn.
Not saying you have to seek out this exact pre/pro as I have for yourself but I think you should try to listen to something, maybe even several preamps and processors to get a better grip of what the potential of the KLF actually is. By the way, I have another buddy that tried this pairing on the Klipsch Owners Facebook group and his findings were very similar to my own. He has even heard similar improvement hooked up to his Paradigm towers...he now owns three different Sherbourn pre/pros that share this chip set. The PT-7020A, a PT-7020C4 and a PT-7030.