Recent 861v4 upgrades are:

linear power supply and 5 year warranty
ID40 -Sooloos endpoint originally introduced for v6
V6 firmware (could be wrong but pretty sure its needed for ID40)

Everything is relative but, G series is budget Meridian, 8xx series is premium product, with premium DAC, with everything optimised for it.

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