Here are several points which I hope are helpful.
1. Your Thiels are difficult speakers to drive. They dip below 4 ohms for part of their frequency spectrum and they aren't very sensitive. If your amp were going to fail on any set of speakers it would be the Thiels. It is entirely possible that the amp was working fine when the seller shipped it to you. It's a 25 year old amp that you put under very stressful conditions.
2. Due to its age the amp needs to be rebuilt including new capacitors. That's going to be expensive - probably well north of $500. In the future you should figure that any amp, preamp, or integrated of over 20 years old needs new capacitors and a thorough tune up. You should figure this cost into your buying decision.
3. I live in central Washington state and I take my electronics to two different shops in the Seattle area that I can personally vouch for. The first is Gig Harbor Audio near Tacoma. They have a very skilled tech who has recapped and repaired my Krell electronics but I think they work on just about anything. Erik (owner) and George (tech) are great to work with. The other option is Condor Electronics in Seattle. They specialize in recording equipment (sounds boards, tape decks, amplifiers, etc.) some of which is quite old with the manufacturer out of business. In other words they are up to the challenge of working on a piece of gear that may not still have OEM parts available. A switch shouldn't fail unless there is a chip that fritzed. I suspect that Condor could fix it.
4. IMO it won't be worth it to repair the Perreaux because even if it is completely refurbished it won't be the proper amp for your Thiels. It's power is not rated below 8 ohms and it only weighs 18 lbs. You really need an amp or integrated that doubles its rated power into 4 ohms. A good example is the Denon PMA 2000IVR (there are several iterations of this amp but all would work). This integrated is a monster (60 lbs) that was made to drive low impedance speakers. A used one in good condition goes for between $500 and $800. The advantage to this amp is that it is new enough so that you won't have to worry about recapping it for another 10 years. Another option is a Krell KAV 300i integrated. These go for around $1000 but if it has not been recapped you will have to figure that into the cost ($700 or so). A third option is to go with Adcom separates like a GFA 555 and an Adcom preamp. Again, depending on the age you should factor in recapping if it hasn't been done already.
5. Finally, I don't think it's a problem to put your speakers on your carpeted floor. I have a pair of Thiel CS6 speakers and they have a similar setup for the binding posts. I have mine sitting on carpet and they have worked just fine.
