Just an update. I see a number of people have read my original post, so I gather some of those same people might be interested in what happened.
While I never got a reply to this subject, I came across a pair of SP1/2Es at a price I couldn't resist. They arrived mid last week so I now have a number of days of direct comparison against my Spendor S8es.
The short story is the SP1/2Es are staying and the S8es are being sold. The SP1/2E bumps the level of midrange clarity and tonal "rightness" up another notch over the already excellent S8e. For they type of listening I do it is a worthy switch.
However, it wasn't a slam dunk. The S8e is superior on the low bass and I'd also give it the edge as the volume goes up. (I don't listen much past 85 dB.) I listen to a lot of acoustic (unamplified) classical, blue-grass and jazz, so that is the primary reason the SP1/2E wins. If pop/rock was the primary type of music I played there is little doubt in my mind I'd stick with the S8e. Simply put, they are both wonderfully musical speakers.