Just to follow up on this - we hooked them up the Maggies yesterday and they work fine. They throw a much bigger soundstage in my room than my Verities, though at six times the frontal area I would expect them to. This is the first time I've ever heard a pair of Maggies and I wasn't sure what to expect. Consistent with their reputation they are very sensitive to small changes in placement, but I didn't find them especially difficult to position for good imaging. They have more bass than I was expecting, though with no physical impact. I've kept my sub in the system and it blends in nicely. The treble seems a little rolled off, and not as detailed as my Verities, but very pleasant nonetheless. The mids are gorgeous, very, very natural sounding piano. On the whole, though they do not have the detail and image focus of my Verities they're lovely sounding speakers. For 31 year old pair of speakers they sound remarkably good. I'm impressed.
As for driving them with tubes, the amp is definitely working harder to drive these speakers and I'm using more of the volume knob, but they seem to be pretty happy together. I haven't tried anything really loud or bombastic, but with the small combo jazz that makes up most of my listening they seem to work very well together.