Krell x-series, are ther any sonic benifits?

well I just sold my krell fpb 200c and I dropped it off at krell for the buyer to have the upgrade done and krell said there is a big diffrence between the two. If there was no diffrence why would they have an upgrade????????

ericbee: great point but being such a large company like they are in regards to sales because they arent a big company in general. I would think that they would stand to lose many loyal customers if the upgrade was a small change in sonic quality. I sold the krell and went back to Levinson