As a fellow Thiel owner, I appreciate your situation. The CS 7 is a terrific speaker but craves a mountain of current and watts to sing right. You can get it with tubes, but quality tube current is seriously expensive (and a continuing retubing cost). You should also consider that your listening preference will further narrow the field. A good many tube amps, when pushed by tough loads, don't offer quite the same bottom octave definition as an SS design. Your room is NOT small, so you'll really need some power to get the SPLs you want from the CS7s. IMHO, the right tube amps for that situation will likely replace your heater too. And I'm talking push-pull - if you want triode mode, well . . . Were you running horns or some other high efficiency speaker, the situation would be entirely different. I've played with many tubes over the years with my Thiels. The EL34s are probably the 'classic' sound for rockers. However, they're not my top choice for durability with a heavy load unless you're going to run a lot of them. I've had the best success with KT-90s - a very rugged tube with fine dynamics. KT-90s are harder to find now. The 6550 is not a bad power tube, linear and a bit 'dryer' than some of the others, and very available. Thiels have a fairly flat impedence curve across the range, which helps. Nevertheless, all being said, I've found my Thiels sound best with an SS power amp and tubed front end. With this arrangement your Thiels will get their fill of watts, yield the detailed and transparent bass slam they're capable of, while retaining much of the fluidity, presence and soundstaging that tubes do best. Thiels are amazingly detailed and do the whole range well - the flip side is that they'll cruelly expose any and every upstream shortcoming. This is why as much as I love tube amps (especially in triode, zero feedback mode), I think it's too difficult a match with the big Thiels. There's a lot of smoother sounding SS gear today - Classe and McCormack are two that immediately come to mind. I thought the old Thresholds were really musical. Musical Fidelity makes a wonderful little SS amp right now, the A3cr, that sounds delightful with the small Thiels, but would be underpowered with the CS7s. With SS power and tubes up front you'll save a lot of money and space, have a much cooler room and get great overall sound. Oh, by the way, run a dedicated circuit for whichever amp you decide upon. Thiels like that.
