OP, I made the move from Forte IIIs to Cornwall IVs. It is a definite upgrade, yet the Fortes are great in their own right. Gutenberg described the CWIVs as a Forte on steroids. I think that's accurate.
CWs give you very accurate bass. I do, however, use them with subwoofers, which is not necessary--just a great next step to take the system to a higher level.
They do great with tubes and surprisingly good solid state. They reproduce what you feed them.
The recommendations above about Volti are good too. They just get super pricey when you option in the real furnishes and features.