After doing many tests, I find that the XA30.8 sounds very very sweet but actually too much. I find it to be a loosely defined amp, somewhat muddy and lacks a lot of air and grip. The soundstage is very closed.
@opm, a few years back I tried to build a second system and wanted to try Klipsch Heritage. I started with Forte IIs and then upgraded to Cornwall IIIs. My main system at the time was based around Revel F52s and a Modwright KWA 100SE amp. I compared the CWIIIs to my Revels and tried various amps (the Modwright, a Bel Canto Class D (based on Klipsch Forum suggestions), and a Primaluna Integrated). I liked the CWIIIs but in the end sold them as they were ultimately too big for my 2nd listening room.
Compared to my Revels I found them to be lacking in high frequency resolution and could not get them to throw a wide or as deep image as the Revels. The latter might have been partly related to the fact my room wasn't big enough to really let them breath. I didn't find them bright at all which was a surprise based on perceptions of horns and reading many forums talking about Klipsch making your ears bleed, etc. My biggest issue with them was they didn't have the high resolution detail I was used to hearing with the Revels. I much preferred them with the Primaluna, the Bel Canto has amazing bass with them but I found the sound dry and sterile while the Modwright sounded musical with them but was a little thin and too noisy; the Primaluna was just right for my ears/tastes.
Since then I sold the Revels and purchased Magico and now Spendor. My amps have been the Pass X250.8 and now the XA30.8. Based on your quote above, my personal opinion is that it is not coming totally from the amp. I'm not suggesting everyone should like the Pass amp sound or it is the best match for your speakers, only that the 'lack of air and grip, and the soundstage is very closed' is what I find the amp does very very well (i.e. throw a very deep front to back soundstage with 3d presence, and at least with my D9s control them with force).
Both my Magicos and Spendors offer more high frequency resolution than the much older F52s did, and both of them disappear in my listening room more than the F52s. Since you didn't specify I'm assuming you have original CWs and not the III or now the IVs, is that correct? I don't know how the high frequency resolution of the CW compares with the III or IV, but presumably there have been improvements made on that front..., and how much better will CWIVs image compared to the original CWs? I certainly didn't purchase the CWs thinking they would image like the modern slim tower speakers.
Personally, I think the X250.8 (or M900u), and dCS BArtok are way overkill for your CWs.
With my easy to drive D9s I found the X250.8 (compared to XA30.8) to offer slightly more detail with a little more speed. I found it sacrificed a little bit of midrange magic and soundstage depth. The XA30.8 driving the D9s into mid dBc range has yet to leave its class A bias for me and controls the D9 very well. I also compared a Bryston 4B3 and Benchmark AHB2 with the X250.8 in my system and found them all to be very close with the 4B3 and AHB2 offering slightly more resolution and maybe speed (Bryston 4B3 had tighter bass with the D9s) but at the cost of the 3d soundstage the Pass is so good at. Maybe that sound would be a little more to your liking and price wise would match better with the CWs. I found the AHB2 is DEAD quiet and incredibly detailed while being musical (with tight bass) so you might try that one, but if you don't think the XA30.8 throws a deep soundstage you might still have issues with these amps in that regard.
If I had the room, I would love to have CWIIIs again (or now the CWIVs) but would match them with equipment more in line with their MSRP and ability to resolve detail; I would likely have tubes somewhere in the chain as well as I really enjoyed how they sounded with the very basic tube integrated I used.
PS: I sold my Pass XP10 for a different preamp (SimAudio 740P) and it made a big difference to my ears so I hear you on the preamp concern; that was with very revealing Magicos and their Beryllium tweeters though, not the CW horn tweeters. Personally I wouldn't have considered that pricy preamp a good value or match with my CWIIIs.
Cheers, and best of luck with your search.