I have looked at the Zu’s as possibility. What about the 12 ohms impedance? Is that an impedance to good sound with my amp?
The smaller Zu models which are 12 ohms (Omen MkII, Omen Bookshelf) are rated at 97 db/1 watt/1 meter. While the XA25’s power capability into 12 ohms will presumably be about 1/3 less than its capability into 8 ohms, that reduction should be more than compensated for by the relatively high efficiency of those speakers. But having no experience with Zu speakers I can’t comment on their sonics.
Also, as Mapman indicated small size, efficiency, and deep bass extension tend to trade off against one another. So a concern with those Zu models may be the adequacy (for your purposes) of their deep bass extension. And I would not judge that by the published bandwidth specs, in part because the bandwidth specs for those models don’t have any +/- tolerance indicated, and in part because we don’t know how much placement-related "room gain" such specs are based on.
Good luck. Regards,
-- Al