Keep an eye out here for used Butlers, they are very good amps with a unique circuit topology.
I would find out what dealers have tube amps available new in your area and audition them. See what brands you like the sound of. Most offerings from a company have a similar type of "house" sound. I would look at maybe Cary, VTL, Manly, Rouge, CJ and see what you like the sound of. You might have a listen to an Audio Research amp also though I don't know that I would call their amps lush. Then look for used amps from the manufacturers you like the sound from.
I will tell you that both Cary and Audio Research have excellent customer service if you need parts or repair. I am sure there are others but these are the ones I have dealt with.
Stereo5, you have tubes in practically all your stuff except the speakers. :)
You might want to take a listen to a hybrid amp (tube input stage, SS output stage), since you have tubes at every other stage already. At least that'll make it easier to get something in the neighborhood of the 175 watts that you've been getting from your venerable Classe.
Brands? van Alstine, Vincent, Counterpoint (used only, but you can get upgrades at altavistaaudio.com), Jolida come to mind. I'm using van Alstine's Ultra 550 and I can definitely hear the influence of those little glowers.
Recently a Cary Rocket 88 R/CAD-808 (30 watts triode; 60 watts ultralinear) was for sale on Audiogon for $1400. I once tried one, bought it, and was converted from large box Naim components to tubes. While not a current model, Cary is great on service and would advise you regarding compatibility with your current preamp. I like buying North American when possible.
Rogue amps and PrimaLuna are also in your price range, and worth auditioning. I own a Modulus pre and used it for 10 years with a Classe CA-200 amp with Vandersteen 3 speakers. I would think Your system already leans to a fairly nice, laid-back sound. When I switched to a tube amp, my choice was the McIntosh MC275, which sounded darn good with the Vandies.
For more richness, you might look at Conrad Johnson gear. The MV-50/52 etc. for instance might be just the ticket for you, and save you some money too versus some of the other suggestions above. You need to be a little careful with the Audible Illusions, since it has relatively high output impedence. You should look for a power amp with higher input impedence. Also, you may be disappointed with the bass you get from your tube amp transition compared to the Classe. Everything's a trade-off, and you need to decide what matters most to you within the money you're willing to pay.
Enjoy the journey!