Krell FPBs are magical with big Thiels. Also consider Pass Labs, Classe' Audio, Bryston, and Parasound JC-1s.
I can see why you feel the CJ isn't quite up the what these speakers require. I had a similar experience/problem and here's how I solved it. Don't get me wrong, I love CJ gear and use a CA200 amp to drive CS2.4s in a second system.
A Krell FPB 400cx (KCT preamp) is what I've been using since 2003 to power my CS6s, this was an upgrade from Bryston 7BST monos. This amp fully controls the CS6 and over the years the bass extension and clarity have so greatly improved that any thoughts I might have had about a sub are now long gone. And over the yers, I believe the amp finished the break-in process of the speakers so that they could fully perform. Also, the mids and highs are sweet and three dimensional' it's hard to imagine improving this, perhaps with a 700cx or their monoblock versions. With this setup there is little, if any, in the way of current limitation from the amp and with the excellent dynamic range afforded by the Krell cx amp, this is what these speakers require to work optimally. Beware: I also in home demoed a 300cx before deciding on the 400cx; the 300cx simply didn't quite have enough juice for the CS6s and the 400cx made a noticeable difference, so for me, it's a minimally required level of amplification for these speakers. Levinson (300 series) and Pass also work well. You do want amps that double power as impedance halves, at least down to 2 Ohms.
See if you can identify the amp that Thiel used to voice these speakers in the design process. I had some older Thiels and was never satisfied until I found that he used Threshold amps and bought some. Problem is in finding out. Most manufacturers don't want to tell you this - they don't want to start wars with hardware manufacturers.
Want to share my experience comparing the Levinson and the Pass. I was a long-time Thiel user (15+ years). I started this hobby with a pair of Thiel 2.2s, then upgraded to a pair of 3.6s. I had paired the 3.6s with the Levinson 333 for 8 years and thought it was a good combo. During that time, the caps in the Levinson blew up on me several times. I finally traded in for a Pass X350.5.
At that point in time, I had been contemplating about upgrading my speakers to Thiel 6 for two years. I was under the impression that with my setup, I had pushed the 3.6s to it's "limit". The sound I got was as good as I could get out of the 3.6s. When I inserted the Pass, not-yet-broken-in, into the system, I could not believe the vast improvement over the Levinson that I was hearing. The bass was deeper and more solid, more extension at the top, and the soundstage was wider/deeper, but more 3-dimensional. At that point, I was seriously reconsidering to keep my speakers. But then, where's the fun. I ended up selling them 3 months later. I didn't get the Thiel 6 as originally planned, but a pair of Verity Parsifal Encores.
I invited a friend, who was very familiar with my system, over that first week, just to make sure I wasn't fooling myself. He went home after the listening session and put his Levinson 432 on Audigon and bought a Pass X350.5 too.
I agree, Sheri was very open and while would not critique my choice she clearly stated they preferred BAT power. I happen to power with McIntosh 1201's with great success, of course had quality gear to accompany them. Placement can vary greatly in the room as always so experiment to optimize. I actually had to stiffen my floor, added cross bracing to the floor joists in my music room and difference was considerable, reverbertions on high power along with dedicated 20 amp lines each amp improved things immensely.
The Rogue will be a high-risk experiment with the Thiel. It may work, or it may not. If you try it, be sure to report your findings.
Personally, I would buy a Pass XA100.5 or XA160.5. If those are too much, go with the X350.5 or the X260.5. Put the tubes in the preamp.
The typical amps to be mated with Thiel have already been mentioned in the post and the archives.
Droz, I understand your goal with the CS6s being increased bass control. These speakers are fully capable of very deep and dynamic bass response but they need to be fully controlled by an amp that can act as an unfazed current source down into the mid 2 Ohm range. This is a matter of physics. There are only a handful of amp designers and manufacturers that can meet this requirement, and, as Rtn1 puts it, these have well been mentioned in the above amplifier listings.
So again, it depends what you are trying to achieve, but I guarantee that the Rogue amps will not do to the Thiels what the Krell FPB series of amps can do for the Thiels, no matter how you slice it. I know, I have tried other amps with these speakers; they are electrically demanding and require stout power supplies that provide sufficient current at low impedances and that property cannot be afforded by tube designs. If you want the bass you cite, this is the direction, high current solid state, that you must go plainly and simply.
Thanks for your input. One of the reasons that I have an interest in the Rogue Audio Zeus is that I have a Rogue Audio Cronus that I very much enjoy. Also, I do have a Thiel SS2 sub, although in my system it seems to add something more at higher volumes. Consequently, I still wonder whether the combination of the Rogue Audio Zeus, Thiel CS6, Conrad Johnson Premier 17LS preamp, and the Thiel subwoofer might give me the potential sonic benefits of tubes and maintain the low end. However, your points are well taken and I remain undecided. If I do decide to go the solid state direction, my main interests would be the Conrad Johnson Premier 350, the Pass Labs X350.5, and the Krell 300/400cx. I know Stevecham speaks very highly of the Krell/CS6 combination, but does anyone have any experience with the CJ Premier 350, Pass Labs, or the Rogue Audio Zeus and the Thiel CS6? Thanks for all of your help.
Droz, I just found this thread - the advice from Thiel owners is spot on. I drive 3.6's with Mcintosh 501 mono's. My final choice was between the Mac's and CJ 350 which btw, is a superb amp. I felt the Mac's were better, more control in the bass for sure and more tonally accurate and pleasing through the midrange. Both have great top end extension. I wanted the CJ to work since I have been using CJ preamps for many years.
I can tell you the difference between my former amp, Classe CA 200 and the Mcintosh mono's is night and day. Thiels are just a different speaker when driven with adequate solid state power.
I have a McCormack DNA-2 Dlx pushing my CS6s. While I am happy with it, I would not call the sound "laid back". I did prefer it to my neighbors Classe twenty five.
I have never heard a Krell amp in my system but would love to some time. I am also interested in hearing a Mac 402.
Some day when I have some extra $.......
I have never heard the CS6 however I have owned a pair CS7.2's for many years now. I used to power them with a Mark levinson No. 333 amp and was very happy with the sound however when I really cranked it up (Rock) it seemed like the 333 was straining a bit and not quite able to put up the goods. Last year I replaced the 333 with a pair of Mark Levinson No.33's Reference amps. These babies don't flinch at all when I crank it up and the base is simply amazing especially at higher volume levels. While the 33's are quite the beasts to deal with (there huge, ridiculously heavy and run very hot when played at higher volumes), if you have the room and the budget I'm sure you will not be disappointed. The one thing I have learned about Thiels' over the years is that the more power you have behind them the better.