Acoustic Zen Crescendo

Wig, my mistake. Your 508 LM is a much more expensive amp that I bet is amazing.  Seems it is also out of my reach. However, congrats on the combo as I am sure it is amazing sounding. 

Zeros are typically used to improve the performance of a high output impedance tube amp with speakers representing a harder load to drive in regards to impedance (and phase angle?).

Better performance is always a plus in my book however performance alone does not necessarily mean better sound which is to a significant extent a largely subjective judgement.

Zeros would add nothing and perhaps even reduce performance used in the wrong cases like with most SS amplifiers that inherently have much lower output impedance than most all tube amps..

I am aware of that Mapman and that is why I am wondering why they were used with the Cresendos are they are 6ohm speakers with steady impedance and tube amp friendly. I suppose OTL amps like 16 ohm loads and perhaps this is the reason? 

Bill,
The 48 watt LM 508ia is less expensive than the 22 watt LM 219ia
The 508ia could possibly be a better match with the Cresendo given the increased power.  My suspicion is both of these LM amplifiers would sound exceptionally good. 
Charles 

Bill,
I get your point regarding the Triode Corp TRX 845 PSET mono blocks,  they are huge and heavy as well as expensive (which is relative). The Triode/Cresendo pairing sounds better than so many amplifier/speaker combinations at the shows that are far more expensive. At CES  3 years consecutively the Triode/Cresendo was among the very best sounding systems regardless of cost that I heard.
Charles