Folks, thanks again for weighing in and sharing your thoughts.
I was just down at Great Infusions yesterday to have them work on my Mara, and I learned that in addition to Rocket, they are also authorized dealers of Quick Mill and La Speziale. I put the question of DBs to Sebastian, their lead tech, and he felt the QM Vetrano 2B would be the best for me given what I'm looking for. Obviously I wouldn't expect him to recommend anything he doesn't sell, although he specifically said that he's had customers bring in Profitecs for service, and he thinks the V2B is more reliable (he couldn't recall which model Profitec he worked on, and his statement may reflect a combination of personal experience and 2nd hand anecdote). Nor did he think the La Speziale Vivaldi outperforms the V2B in a home setting, though he did say that it handles higher volumes, and also that it's a more forgiving machine (requires less attention to pour a good shot). Finally, Writer, I saw a confirmation posted on the "Bianca-fy" thread that the QM machines are compatible with it, so that would be a possible future upgrade path. Yes, I would like to improve my own tech skills, but many of my problems on the Mara have been electrical.
Anyhow, the Mara seems to be working without issue for the moment (3rd p-stat replacement, air blown through tubes to clear out any scale flakes, and adjustments to both safety and OPV valves). Fortunately more signs of corrosion. This upgrade is going to happen sooner or later, but I'm going to be very deliberate. Or perhaps I'll see if I can convince him to take it as a trade-up