Looking for advice on these speakers

Al,
The saving grace is that the "vast" majority of recordings won't approach the 50 db dynamic range. Genre of music, room size and typical listening levels will determine sufficient power needs . classical and jazz seem to have less compression and thus a broader dynamic range in their recordings. Most pop and rock recordings are generally much more compressed as you noted. 8 watts is fine for my needs and listening levels but may not be for another listener. Another consideration is quality level of the SET amp (transfomers and power supply). One 8 watt amp could struggle while another sounds effortless.
Charles,

What Al said but DR constraints likely extend to other genres as well with good quality recordings.

HE speaker manufacturers often underplay this issue in order to demonstrate their speakers with low power SETs. Results are OK but may be limited dynamically compared to the best. Zu is one maker I have heard where a demo fell flat and the Zu guy admitted the SET was probably underpowered for the rock/pop material being demoed.

Maybe with the absolute most efficient horn designs, like say Avantgarde, if things are going well.

Mapman,
I'll disagree with you on this point. The example Al cited of dynamic range
45-55db is actually quite rare for the overwhelming# of recordings ( his are
very special cases). My 8 watt SET replaced my 100 watt push pull tube
amp well over 4 years ago, it simply outperformed it. Dynamics, authority,
overall scale are very, very cose ( minimal loss) all other parameters
improved noticeably, tone, nuance, inner detail, presence and most
importantly, naturalness. If this weren't so I'd gone back to the 100watt
amp. So much is predicated on the speaker involved. Some of this really
depends on preferred listening volume, my SET can go louder than what I
care to listen to.

What was and remains highly successful for me may not be for others
(that's
true of most anything). My jazz and big band recordings have comparable
dynamic range to classical music and more than most rock and pop
recordings. When I do play orchestral music it is very involving and
satisfying. I know of others who've had the same happy results as me in
this type of switch. Again each of us may have different experiences and
will choose based on that knowledge. All I can say is in my case the 8 watt
amplifier is an unquestionable upward move and there's no looking back.
I can't speak to your Zu example obviously, I wasn't there. Many happy Zu
users on this forum would probably give a different account of their
experiences. The truth is lower power amplifiers won't be the answer for
everyone and the same can be said for higher power amps. There are quite
a few people on this forum who listen to multiple genres of music and are
well satisfied with their low power amps.
Charles,

Charles, yes, I think it all depends case by case as usual when it comes to what is good or good enough versus not as good....a lot is always a judgement call plus no two combos are exactly the same.

The key is always knowing what your goals are and working to achieve them. Lots of ways to skin the cat. You never know for sure until you hear.

Mapman,
You summed it up succinctly and I agree with you. This audio quest is an individual pursuit for certain.
Charles,