Cary 300SEI w/Harbeth P3SR or Spendor SA-1?

You will be fine with those speakers.

Both the SA-1 and P3SR are less efficient than your larger SP1/2E. (SP1/2 is 88 dB at 1 watt, the SA-1 is 85 dB and the P3ESR is 83.5 dB according to specs.)

Assuming you are reasonably accurate about your maximum desired volume you'll probably be OK, but it will take more from the Cary amps than now needed to reach the same volume.

You might want to invest in a $50 sound level meter from Radio Shack to get an idea of your real listening volume in the room. A lot of people over and under-estimate how loud they listen.

It is not about SPL level.
The real problem is dynamic congestion & lack of nuance.
The transients would be dull, the highs filtered & the midrange would not open.
The transparent live event would be absent.
The rythm, timing & soundstage maybe not.
But this is not the proper way to proceed if you accept loosing all those precious values form the start.
I would prefer a Proac Response 1SC

George

It is not about SPL level.
The real problem is dynamic congestion & lack of nuance.

I'll have to disagree. Desired SPL levels are a very basic factor in amp/speaker compatibility. It's rather like claiming horsepower or torque are meaningless measures for a car engine. Just because there is more than one factor to consider doesn't render a fundamental measure irrelevant.

Dynamic congestion certainly becomes an issue if the amp is being called to deliver power it doesn't have on the transients. That is inevitably tied back in one form or another to speaker efficiency versus available amp power. Far too many people are perfectly satisfied with SET amps to automatically discount their suitability in this situation without further examination.

Similarly, far too many people overstate the dynamic range of recordings. When you're playing back a loud section of a piece of music, with rare exception for a few specialty recordings, there just isn't another 15 or 20 dB of dynamic range hidden in the background. That is why it becomes important to have an accurate reference point for the average desired volume.

I've seen some people describe an average level 75 dB as "loud" while I've seen others listen at 95 dB and still want to crank it further. So when the original poster uses the term "moderately loud", I have no idea what that really means in his case.

But, if one can take the phrase "absolutely splendid" at face value, it certainly seems he is well satisfied with the amp in combo with his current speakers. If he's running his current amp close to the edge, he might well be disappointed with the different speakers. Or, if his amp is still coasting in the current setup, he might be very happy with the speaker change.

Thanks for the thoughts all.

I spoke by phone with a very knowledgable dealer of Spendor and Harbeth and Cary. He says I'd be you-know-what in the wind! Just wouldn't get the most of the things.