I was wondering the same thing. I had a C2300 and replaced it with a Audio Research LS28SE which was a dramatic improvement. Basically, there is an entire world of detail that the C2300 simply can't resolve. I was wondering if the C2800 would have a sonic improvement over the C2300 and asked Mcintosh this question but have not heard back yet.
Mcintosh C2800 and C55
I saw that Mcintosh just came out with 2 new preamps. What are your thoughts on these units based on the specs? Any reason to upgrade from the C2700 or C53?