So I sent the Prologue 16 back, after two weeks of putting up with unusual tuning gremlins in the lower octaves / random squawks in the middle range. It's just not yet ready for live performance, and surely not complete, in the QC sense of the word.
If those issues are resolved in the future, perhaps I'll consider a used 8-voice unit, but frankly, after some comparisons with other gear, the overall tone just isn't there (in spite of the differences due to the 2-pole filter). I'm purely speculating, but I think that the digital FX section is always in-circuit; that might account for the lack of headroom with more complex patches.
The spec is great, but the execution leaves much to be desired-which (as an aside) is going to make life somewhat complicated / "interesting" for the Korg USA folks, now that they're distributing Waldorf as well.
What I replaced it with, on the other hand...
...see profile change!