what you have now is synergy between your components and synergy between your speakers and your ears. Once you change it the synergy may be gone. With new speakers you may need to change another component... maybe not. For one the KHLs have a higher sensitivity.
For the price of the Harbeths you could try a lot of different speakers. It's not clear to me if you are just curious about the Harbeths or anything that would provide you with something more and different than the KHLs. There are better values for the money, British speakers in the US are usually pricey