Dynaudio Sapphires ('11 demos) were a huge jump over older (ca '95) ML SL3s.
Raidho D2s in ('16 used) were just as huge a jump in sound quality difference.
But, bang for the buck, nothing has ever touched the improvement the (cheap) DSPeaker Anti-Mode 2.0 made to an already enjoyable system. Night and day after the bass humps are removed (I can't/choose not to alter walls/windows). It's adjustments/corrections allowed the speakers to really shine. I'd never go back.