Autoll, I can't help you out about the differences between the Cam-400's and the Cam-350's, but I can share the following information regarding the Cam-350's. About three years ago I went through a long audition process, which included seven different amps, and finally decided that in my system the two best amps were the Cam-350 mono-blocks and the Edge NL-10. The Cam-350's were detailed, dynamic,excellent top/bottom extension and were very smooth and silky. I thought the EdgeNL-10 did everything somewhat better, but it also cost $5000.00 more then the Classe amps. I could have easly lived with and enjoyed the Cam-350's, but was lucky enough that I could spend the extra money on the Edge to get a higher level of performance. So, if you can get a good used pair of these beautifully built and wonderful sounding amps at a good price, I would go for it. I believe you would have to spend another $3500.00 to $4500.00 dollars to get a much better sounding amp on todays market. An example would be an amp like the new Pass LabsX-250.5, which is a great sounding piece, but would cost you alot more money, and doesnot make the Classe amps sound like "chopped liver" by any means.
