I'll agree with Jameswei to some extent, with a caveat and an observation. The 3.5s are still good sounding speakers, and can use a good powerful amp to drive them, but their tonal balance is tilted towards the treble and thus care should be taken to choose an amp that's not going to come across as too "hot" on top if you go with solid state. When I bought my Krell KSA 80 years ago, I listened to it (admittedly not yet broken in) on a pair of 3.5s to get an idea of its sound (I was getting the amp for my Duntechs, which this dealer did not carry, and the Thiels were the only speaker he had with which I was familiar, having previously owned Thiel CS3s). The sound was OK, and sufficed for my purposes of being sure the 80 had enough power and bass control for me, but not broken in the Krell sounded quite hard and bright on the top end. As I was leaving the store, they had just hooked up a Conrad Johnson Premiere 3 (I think it was the 3, it was their top of the line then) to the Thiels for another customer, and I had to stop and come back to listen for the sheer enjoyment of it when I heard that combination. Yes, the bass wasn't nearly as controlled, and perhaps the highs were rolled off, but what a great midrange and soundstage! My first exposure to tubes, which within two years replaced my solid state equipment. So don't be too quick to write off tubed equipment on the Thiels, just make sure it has enough power to control the speaker. A final point, there are some who believe that the 3.5's equalizer to boost its bass is the weak point of the design (there were mods available from JPS, I think, among others, to improve the equalizer); if you don't listen to a ton of organ music you might want to experiment with the EQ in and out of the system to see if the added transparency without the EQ is worth the tradeoff in the last octave of bass extension. Good luck, I think you'll enjoy your time with the Thiels!
