I would guess it doesn't matter whether the ac12 sits with the kit or at the speaker. It's unlikely to have flying leads out of it so it's going to be down to the what flying leads you use - a short bit of speakerlink and existing long m/s lead (ac12 at kit) or long speakerlink and short m/s lead. The connectors on the ac12 would be the same for both.

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