The Alex Duetto II meets all of your criteria. E-61, PID dual boilers, easily switched to plumbed in or tank fed, temp stable, etc. I just received my new Duetto the other day and am still getting used to it. See my
short review/initial impression thread. In summary, it's a good machine, but with a few odd quirks.
Also, be aware that the Vivaldi cannot be switched from plumb in to tank or vice versa. There are two separate versions, one that is plumb in only with a rotary pump, and one that is tank fed only with a vibe pump. Also, Vivaldis don't have a true PID, though they have an electronic thermostat that works quite well. By all accounts, the Vivaldi is an excellent machine, but you do have to commit to one style or the other.
I haven't seen or used the VBM DD, but it sounds like a very nice machine too.
Really, I think any of these machines would do great. Which one you choose depends more on individual taste than any objective criteria.