Hi Roy

Personally,i doubt it.SF never sounded "tubey" ! The sound you love comes from all the other components in your system not from your power amp.

Boy, I hate to hear the words "tube sound" because that implies you are hearing something that you feel isn't available with transistors. Since the goal is somewhere between what is pleasant sounding to your ears and what is closest to the reality of the original, "tube sound" always seems to indicate you expect some sort of magic from tubes that you ascribe to the tubes themself. (For the record, I use tubes in my pre amp and power amp, and I have used this set up for more than two decades. But my speakers are very tube friendly.) When in reality, "tube sound", as I know it when tubes are paired with Thiels,is more the result of those big old output transformers on the back end of your amplifier and the way tubes operate compared to transistors. Your speakers can almost always use some "softness" or neutrality at the high frequencies and when I hear tubes and Thiels I immediately think you are using the tubes to tame the high end of the speakers. Which is all well and good , if that's your goal, since liking what you own is the final "decider" and Thiels can often times sound excellent with most well built tube amps.

But most tube amps and Thiels are not a good match. Not because of the power in shear wattage that you can find in most tube amps, but because of the load the Thiels show the amp and the nature of tube power amps.

Thiels and tubes are seldom at their best together due to the complex load of the Thiels, which makes you always think you need more "power". You need more current when driving Thiels. The phase angle of the Thiels, and the sometimes complex impedance load of the Thiel crossover, requires an amplifier that can slug through a multitude of small value inductors and capacitors used in the crossover's correction network(s) using some good old fashion amperage. Most tube amps can't deal well with this load since, as a rule, tubes are more current limited than most solid state amps until you are spending large sums of money for your tubes. Despite the momentary flashes of brilliance you will hear with Thiels and tubes, I think you will do better with a solid state amplifier. Save the SF for some LS3/5a's.

Keep the amp as close to that "tube sound" as your concept of neutral will permit and you should find the Thiels are much happier and you will not be feeling the need for more power, if the power you provide can deliver the amperage the speakers need. My choice would be Rowland or McIntosh but the BAT would likely do well also. Remember, it's not the power in terms of watts. 80 to 125 watts alone isn't going to be that noticeable as an upgrade. But keep the amp pumping current into the Thiel's crossover and the speakers will be happy. Will you loose some of the "tube sound" by going this route? Probably, but you have more than enough to go around and the "tube sound" you loose will be your current amplifier struggling to make a go of it with the Thiels. Expect something different that what you have, that's why you're making a change, and you should be pleasantly surprised.

Roy,i would like to suggest a power amplifier.I understand once you are used with tubes,you are afraid to go solid state.Unless you have a friendly dealer there,try Quicksilver v4 monoblocks.Excellent sound/service/customer support and as far as i know,a pair costs less than $5000.