1. If you want it NOW- then it is the right time to buy ASAP smile. I have no idea about timing of next gen 861 but I expect this will be Q1'17 release (maybe with announcements made earlier).

2. If you want Bluray/lossless LPCM then you have no choice but to use HDMI out of source and for this have to add HD621. If you are ok with lossy DD/DTS or 24/96 format then you can continue to use Coax Dig out without requiring HD621.

3. I agree though G55 is no slouch. You can use any of 'good' options or try your hand at recent Class D multichannel amps. Let your ears decide but not our opinion smile

4.Not compared sonic qualities but ID41/Sooloos provides for more elegant solution - and you will also need Sooloos core component if I recall between your NAS and 861.

If you have Atmos/Auro/front height speaker set up and want a processor now- skip 861 -it does not offer any support now.

For traditional 5.1/7.2 I would recommend you to buy demo 861v6 or 861v8-IMHO once you take 2 channel Sooloos+HT- I found 861 worthwhile premium over other brand models. You would have choice to upgrade (or trade-in) once newer version of 861 became available from dealer you gave business to smile


Regards,
Kishore