I don't believe that Meridian is a 'reasonably closed system'. The only thing within a M system that requires another M box is MHR smartlink ie DVD to Processor and this is no different to say Denon with Denonlink and that would never be classed as being a closed system.

Everything else can be linked to pretty much anything else, including DSP speakers as long as the source has a digital out.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).