Why use the V2 or V3 at all? Do you hear a difference between its AD converter and that in the 722?
Good question. The answer is yes, depending. I definitely hear a difference in the V3 AD and would hope to hear a big difference in the ACM V3 compared to the 722 AD. More important question to me is the V2 in front of 722. What purpose would this serve? Different flavor?
IMO, I would use either the V3 or ACM V3 > digi > 722. If you like the analog inputs of the 722, you could skip the V3s.
But in the end, I think you should reduce the number of analog steps as much as possible, and go for what sounds best to you.
For 99% of listeners out there (like me), there will be no difference in how it sounds.
I've been doing Nak > ACM Tascam HD-P2, and I've been very happy with the results.
Terry