Unfortunatelly new dimention is the problem of every audiophile. Simply because there is ALWAYS new dimention.
I also was a big Pro Ac fan for years, and owned Studio 100, and later Responce 2.5, also with Cary, but not with SET.
I noticed, with time, that I do develop listening fatigue from Pro-Acs.
My next step was Kharma Ceramique FE 3.2 with Tenor 75W OTL. That was different in all ways, with no comparison to any Pro-Ac speakers you audition, incl Responce 5, and to any Cary SET respectively. I do, personally, think that Tenor OTL are Best ever made monoblocks in the world.
FE 3.2 are Kharma most successfull desighn (and one of the cheaper ones), at least in Ceramique range. My search for preamp was painfull, long, and difficult, but finally I bought Wavac PR-T1.
CD player is Gamut CD 1, but this is due to change at some stage, as Gamut transport is not reliable, and, unfortunatelly, not fixable. What CD player I want?
At this stage, I am waiting for Zanden to make single CD player, but checking for Metronome or Audio Aero.
All above can be called ultra Hi-End system, but there are some recordings (especially small scale, and female Jazz vocals) that do sound amazing, but some (larger scale orchestral) are lacking (a bit).
Just recently we with a friend placed Kharma and Avalon Einolon side to side. Einolons did oposite to what Kharma did. They are big, but difficult to drive, even with your SET. The choice is the preference, but not quality of one over the other.
Soon I will post pics of my room, and some acoustic make-up I am trying (currently) to apply.
In re to your system, I think that Cary SET is your main component I will not change.
From there you can upgrade any way you'd like. Some found combo of Lamm SET with Wilson speakers to be the winner. You can try Watt Puppies with your Cary. Audition them, and you will notice how nice your Cary SET really are. In re to cables: I used Stereovox Ref interconects and speaker cable with Cary/Pro-Ac and results were very good, and I do keep them with my current system. Elrod ribons are usually paired with Tenors, but they are very good with any tubes. Both cables are not overpriced.
Stand wise. Fenite Elemente will make the difference at some stage. It is very hard to DIY the stand that will match FE.
However....
If you do enjoy the music at present, then leave it as is for as long as possible, because sooner or later you must upgrade. That is how the new dimentions are born, and how it works in audiophile world.
Enjoy the music.
Alex.
