Harbeth Super 5s vs 5+s

Hi all. I am at the stage of finalising my system. I currently have Harbeth Super5HLs as my speakers (with a Concert Fidelityy pre and Lamm 1.2 Refs in).

I have an opportunity to change from my current Harbeths Super5s to 5+s - but it will cost me around $3400 US net to make the change. How much of a difference is there between the previous Super 5s and the new 5+s? I'm just trying to decide if it's worth the extra $ outlay.

Thanks in advance for any thoughts.