Hi again

I've made the assumption that you are looking at a used purchase, so you ideally want to find a v4, as it's the sweetspot in terms of performance/price/recent updates. That would give you the IE42, the more recent DACs in the analogue output cards, room correction, compatibility with the Sooloos system if you add the ID40 card, and the possibility to renew the overall warranty for another five years along with the PSU upgrade.

The IE44 card you mention is from the 861v6, and as the more recent model, I'd guess there are fewer on the used market, and they will cost more. They require the OA08 unbalanced or OA18 balanced cards for analogue output.

It's worth noting that the HD621 can output with either three SPDIF lines or one RJ45 type MMHR cable. The 861v4 with IE42 will use the three SPDIF connections, the 861v6 and v8 (current version) will use the network type MMHR cable.

MHR is Meridian's own encryption for 88k and 96k signals, and is used whether the signal comes in via SPDIF or the MMHR connector.

Cheers

George