Cornwall III's can sound dull, muted and warm with many amps/preamps. The new IV is much more alive, lively and sharp. I love my pass gear with Heresy IV and LaScala. Gorgeous, huge soundstage and sweetness that tames the highs of these speakers. The VIII's from Klipsch were much more dull sounding than what they make today.
I have a set of XA60.8's and an XP-10 running Klipsch version IV's as well as Fleetwood Deville's. The sound is the best I have had in 35 years of HiFi. I know a pre-amp upgrade will improve it further as the XP-10 does lean slightly warm, Even so the sound is wide open and huge.
The #1 ingredient to a great system is the room, then the speakers, then the pre-amp/amp, then the source/dac. Then cables. The kicker is....synergy. Add in something that doesn't have synergy when all connected together and it can sound awful.
I wouldn't trade my Pass Labs for any other gear as I have not head anything better in my space, with my gear. But for others it may sound dull, lacking or even bright. All depends on the synergy.
If you want a nice wide open soundstage, the Heresy IV will do much better with your pass gear than the CWIII. They can do big, sweet soundstage. They are not bright nor warm. They image like mad and sound stunning with Pass Labs. The 30.8 would sound gorgeous with them if they were set up right. Also, you have a world class DAC but it also leans warm. You have a warm amp, warm DAC and warm speakers. Yes, CWIII lean warm and muted.
I believe if you changed your speakers you would be much happier. The Fleetwood Deville's are a huge step up even from my LaScala in every area. Even something like a set of KEF LS50 could bring you what you look for. Dynaudio bookshelf. B&W also can be fantastic.
The gear you have far outclasses your speakers here. Even moving to Cornwall IV would shock you as they are much better than the III. Bottom line is that you have world class electronics. The synergy with the speakers is off.