I used to have 3.5s and drove them with a Classe CA-200 amplifier that is 200@8 and 400@4. I don’t think it was enough power. Keep your eye on the EQ box. Mine would periodically go out of whack and put the amp into protection mode. Each time it got temperamental, it had to go back for adjustments. I think I had to send it back three or four times. Then I had a mid driver go, so both of them went back for a rebuild. The drivers are not an off-the-shelf part and they’re no longer available, and with Thiel gone now, I’m not sure if they’re rebuildable anymore. I’m just sharing my experience and not trying to scare you at all. You may have good luck with yours.
Due to all the issues and with Thiel (the company) going to crap, I decided that the only option was to send them on their way. It was the best move I ever made as I have at least four times (maybe more) better sound now with all the same electronics. My new used speakers were about 4 times the cost of the used 3.5s, though, but they were still relatively inexpensive and totally worth freeing myself of the 3.5s.
