Should I upgrade my Krell FPB 200c to cx300?

Well, you actually sort of lose either way. If you don't upgrade, you'll be wondering how much better it would have sounded. If you do upgrade, you're out the cash.

A third alternative is to send the amp to me. This costs less than an upgrade and solves all those nagging problems with voices in your head talking about "CAST" and "dynamic envelopes" and "authority". I certainly wouldn't call you up and talk about that stuff. The amp would also sound better over here than at your house. Let me know.

Mcx also optimizes balanced inputs by speeding up non CAST connections to make them sound much faster than non Mcx non cast connections. Don't sweat the tube pre, I'm sure it sounds fine. You don't need to have all cast to benefit, but when you do it is cumulative. If you are looking for addt'l speed and a slight increase in smoothness on top and midrange, consider it, if not then you won't miss it much, especially if you're already digging what you hear. Out of curiousity, what is your pre?

Thank you all. I appreciate your help. To answer some of the questions listed above, I currently use no preamp. I am running the new Resolution Audio Opus 21 balanced direct to the fpb 200c. I had the KRC-3 and it did a fine job. But the direct route is more revealing and I preferred it in the end. The cost of the upgrade to cx300 is about $1,700.