Anyone knows the Classe CA-401?

I'd suggest the Spectron Audio Musician III SE Mk2. It is a very musical amp with tremendous headroom and extention and almost 'tube-like' but without the 'veil'. It will drive any and the most demanding speakers including your Thiels.

Classe equipment was used to demo with Thiel speakers at a lot of audio shows that I had attended in late 1990s and early 2000s. Can't remember exactly how they sound, but I believe there is some synergy there.

If you are using the X1, why not go with a X250.5 or X350.5. I had lived with a pair of Thiel 3.6 for over 10 years. I had powered them with a Mark Levinson #333 most of that time. Due to some reliability issues, I had replaced the amp with an X350.5 last year. Out of the box, the X350.5 sounded amazingly good. I was dumbfounded as I had thought with my system that I had pretty much "got the most out of" these Thiels. With the Pass, I got deeper and more controlled bass, more extension in the treble. The soundstage extended behind the speakers and also wider/bigger. The the midrange had that special sparkle that you get from tube amps.

Up to that point, I had been contemplating upgrading my speakers for over two years. After I inserted the X350.5 into the system. I seriously thought about keeping the Thiels. But then, where's the fun if you don't play with more toys. Currently, I have a pair of Verity Parsifal Encores. As good as the Thiels were, I am very happy with these.

FrankC

I owned the CA-400 for a few years which drove Martin Logan Quest speakers. Nice amp, I really liked it a lot; a real brute, never ran out of steam, very controlled bass. Although not a tube sound, I thought the midrange and top were quite good. Very well made. Not sure what the difference in the 401 is.

No one else listened this Classe CA-401?

A friend had the 401's and I had the 201's. Both of us used them on Magnepan 3.6's. We like both Classe's very much - tons of power, detailed, smooth, very well built, fine value for the money. But, good as they were, they were significantly exceeded in all respects by Pass Labs amps, as Gundam91 said above, and I agree with him totally. My friend got the Pass 250.5, I got the 150.5. The sound improved substantially v. the Classe's. Sorry to tell you that if you're really thinking of the Classe 401. BTW, the Pass amps are VERY conservatively rated in watt output. My friends 250.5 (250 wpc@8 ohms) just about equalled the Classe's 400 wpc. My 150.5 (150wpc) easily equalled the Classe 201's 200 wpc.