How loud do you listen?
SPL at the listening position.

Hi John,

Welcome to the forums!

90dB speakers are not impossible to use with a 2.3 watt Zen, but less than ideal.  The reason is that in order to hit your modest listening volume at a distance of 10' the amp will have to be turned up basically as high as it can go without clipping.   The means that whenever you want to turn it up louder, you won't be able to.

I ran 90dB speakers with a 2.3 watt Zen Triode for over 2 years when all this started in the early 1990's.  It was fine 90% of the time.  The other 10% a little frustrating.  BIG TAKEAWAY here is that I had not heard the speakers I was using on more power.  Had I come off of 350 watts down to 2.3 I just wouldn't have been able to deal with it for as long.

There are two things to consider here -

1) the magic volume when it feels right will come much sooner as you rotate the volume control with a Zen Amp.
2) speakers will disappear better - to a point where they can be pulled as close as 4 feet from your face, pointed right at your head, and with your eyes closed would sound like they were apron 20 feet away in a huge space.

If you willing to deal with these things, then a single amp or even two amps bridged would be ok with those speakers.  It would sound incredible until you run out of power.  The experience would change priorities.  You would find yourself serious about either getting more power or more efficient speakers.

Steve

Also, what about going with one of the TORIIs or the Mystery amp ... I am assume the more watts would make a difference, and I'm assuming the auditory experience is at least similar to the lower watt amps.

That is what I would be looking at if I were you.

Personally I wouldn't spend twice the money for a 3 dB gain (and double the circuitry).