jeffvegas
Should I buy used Thiel CS5
If they are in good condition, a definite yes, as even by today’s standards one of the greats, but only if driven from an amp that is stable and can deliver big current into 2ohm continuously and remain comfortable doing it.
Stay away from tubes, most Mosfets, and Class-D "if" you want to get the very best out of them, read here.
https://forum.audiogon.com/discussions/what-class-d-amps-will-drive-a-2-ohm-load
Cheers George