Th G65 is not that dissimilar to the G68, I assume you compared configs?

Maybe just try the analogue or digital out of the MS00 for starters?

Are you getting sound when using the calibration function? That would confirm your speakers are hooked up correctly.

[edit]
Of course I am also curious about any differences you experience once it is all up and running?

And would suggest comparing old depth\width center Trifield settings once things are up.

Meridian G68 AXV, HD621 | Cinepro 2k6mk5 | 4x Scanspeak A4 monitors, center & 26W Sub | RPi Hifiberry digi+ | Roon