jonandfamily, It's been a long time since I've heard the CS 1's. I believe they were a very steady 4 Ohm load of moderate sensitivity. All in all a pretty easy load for most amps, providing of course they are suitable into 4 Ohm loads. If one plans on using tubes, it's suggested to double the power rating. As I recall, they were of typical Thiel sound, but due to the limited bass, could sound more tilted up.