Beernut, regarding the sound of the Zu's:
Compared to my Vandy 3a sigs(which are a bit like your Maggies), the sound is a bit more 'forward', I notice more 'inner voices', too.
Sound isn't fatiguing. My Unions sound good without a sub, but I believe they sound better with one or two- More a matter of physics, those cabinets aren't very large or heavy.
Do you have an idea which model you want?