I owned a Rawson F4 clone and paired it with the original Zu Druids. It sounded amazing at low volumes but ran out of steam quickly as you turned it up. The 16 ohm Druids definitely cut into the power delivery, and since the F4 only increases current you need a very high gain preamp. At the time I didn't have any other speakers to try, and decided long term to keep the Druids rather than the F4.
In the right system I'm sure it's stellar.