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

Russ +. Nailed it.

Three out four of yours are good choices for new speakers.

I am buying one of them now.

I would swap the SF Olympica for the Amator Electa III.

That would be my ideal choice of those 4. Add a couple nice little RELs

and you are up by 200% from where you are now.

I just changed to a Coda Continuum 8 with my Kef reference 3. It makes beautiful  music. 

Thank you, everyone, for sharing your experiences and recommendations. You have given me plenty of food for thought. I will see what changes the Rogue preamp brings and then make some decisions. If I can remember I will update this thread but it likely will be 6 months or more.

...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).

@atmasphere Thanks! The Spatial X5 are really terrific speakers. Clayton and his crew have done a wonderful job with them. And I know they particularly shine with tube amps. But they just were not right for my situation.

One correction: the Spatial's were five feet from the front wall. And they sounded wonderful... if you sat in the very narrow window of a sweet spot. Most natural sounding tweeter I ever heard. But stand up? Lose all HF. Pour on some power? My perception is they don't scale well. And even with self-powered 12 inch woofers they didn't energize the (rather large) room as well as I like.

Mine is not a dedicated listening room. It is a combination living, dining, and kitchen at 25 x 25 x 8 feet. I have music on almost all the time, as I work in the kitchen, eat dinner, read, compute, or less often just sitting to listen. But I want to enjoy satisfying reproduction whatever I am doing. In this situation the KEF Reference is getting me closer to where I want to be, but there is still room for improvement.