Higher powered but efficient amp with the imaging of a Pass XA-25?

@markmuse If I were in your situation, I would first talk to Duke at Audiokinesis and get a set of his Swarm subs. They would allow you to have proper bass anywhere in the room. The Swarm is 4 subs so as to break up standing waves that otherwise cause bass nulls to appear in the room, often at the listening position. They also prevent too much bass elsewhere in the room.

That would free you up to use a smaller speaker since the Swarms are good up to about 50-60Hz. That would open up a lot of possibilities for easy to drive speakers; if they are easy to drive the amps don't have to be as powerful, and often the smaller amps are the better sounding ones.

...I had an XA-25 for a trial driving a pair of Spatial X5’s (97db efficiency). That combo produced imaging depth like I have never heard before or since.

The Spatial is an excellent speaker and easy to drive. But since you have to keep the speakers closer to the wall behind them, its probably not a good idea to use a speaker with rear-firing information. If less than about 5 feet to the wall behind the speaker, the reflected information will be interpreted by the ear as harshness rather than imaging detail.

But I think if you liked the Pass, going to a more efficient, easy to drive speaker is the way to go. All amps make more distortion driving difficult loads! This causes them to sound less musical.

With most amps out there, you'll find that tube amps do a better job of imaging and depth than most transistor amps. So the tip about keeping the speaker easy to drive will play very well into the idea of a tube amp if you go in that direction; it will also work nicely with the Pass if you still have it (that amp is fairly low power so you'll need a speaker that has efficiency in the high 90s, like the ZU Audio stuff).