861v2 and under I have no direct experience with - I am not sure if they will do DVD-Audio or interface with HD621. If you are looking for DD, DTS and stereo inputs I guess it is an affordable entry point, but older.

861v3 is configured with the "old" configuration app, I used one for a while with an HD621 and it worked OK until I could get it upgraded to v4. It was a little tricky to get to work right but I got it to work. Sounded good, no problems, but tricky to configure (no suprise as it the old config app was released waaaay before the HD621.

861v4 is configured with the current config app, Meridian has released its apodising firmware (6.03) and is the most widely available currently on the used market. I think they sound brilliant and have 2 smile

861v6 is a redesign, no direct HW upgrade from 4 to 6 . If you love listening to music, a v6 is definitely a strong step forward for music playback, plus it has the option for a ID40 card, which directly plays back Sooloos music, with a network interface.

Primary: 818v3+ID41, M6 stereo pair, M SpeakerLink cabling, Sonos+96kHz Cullen, silver DSW
HT: Marantz prepro, 271, DSP3300, 8K SE FL/FR pair, DSP M6x2, DSP320x4 (ceiling), black DSW, 520 RL/RR rear in-walls
Living Room: G65, 640 L/R in-walls, UHD722, MS600
Vac. Home: G61, HD621, 4xDSP3100, DSP3100HC
MDMS:NUC/ROCK+TrueNAS Core 12.0 ZFS file server