I was reading the processor 101 and HD621 WIKI's and it is not clear to me what would be the minimum version entry point in terms of functionality for an 861.

Is there a document somewhere or can someone explain what improvements were made with each version 1-6? Do all versions work with the HD621 or only 4 and 6? I was thinking of getting an Oppo universal player and use the HD621 to connect via HDMI so I could do HD blu-ray audio, SACD, DVD-A stuff.

On Audiogon right now there are version 2, 3, 4s for sale with widely varying asking prices.

If you were going to buy a used 861 which version at minimum and why?

Thanks, Al

Bryston SP3 processor, Bryston PP300SST monoblocks x3, Dynaudio Confidence 5 speakers LR, Dynaudio Excite X28 center speaker, Apple TV4K, Samsung TV.