I now have the Oppo 95 connected by digital coax for DVD and analogue phono's for CD replay.
This is the wrong way round.
As you don't have a HD621 yet, you should set it up this way:
For CD / DVD (2 channel PCM & DD/DTS bit streams):
Oppo -- Coax --> G68 (say input D1, note note MD1 as this is for multi-channel)
For BD (hi-res codex tracks)
Oppo ---six channel analogue---> G68 analogue inputs (configured on G68 for multi-channel)
Do you use Mconfig (you should realy to get the most out of the G68)?
If so you can put all your equipment in that and configure up the connections, then download the config to the G68.
Regards,
Carl