PSB Synchrony One Speakers and Pass XA30.5 Amp

I typically listen at very moderate levels and the lack of dynamics to which I refer are at such levels. I wouldn't have thought insufficient power would be an issue at such moderate levels (the bias meter on the amplifier barely moves.) And although the Pass is rated at 30W/channel into 8 ohms it is much more powerful than those 30W a side suggest.

@partialresponse , I would think that the Pass XA30.5 could drive this speaker with its high current, but there have been past threads where somebody had described the same situation with the Synchrony One. Basically complaints of lifeless or non engaging music.
This is a demanding load where impedance drops to 3 ohms and below. The speaker is rated at 4 ohms, so the Pass should double down to 60 wpc/4, correct?

Maybe it doesn’t pair well with Class A, just a guess.

It seems like you are listening in a near-field setup, so room acoustics may not have an effect. Make sure the speakers are at least 3 ft. from front wall and play with distance from side walls. I needed speakers to be 7 to 8 ft. apart and toed-in.

Are you getting 3D imaging and wide soundstaging? You should be with that amp.
Lastly, what are your speaker cables?

Did the PSBs ever have the vitality you want, driven by any other amp?  If so you know they can do it,.  Now you have to decide whether you want to design the rest of system to get that out of them.  I went through that with some Focal Electras and was quite happy with the result.  It literally to years of trial and error to get there  though.  If you haven't heard them do it in another system then I would ditch the PSBs, and go on the "perfect speaker" hunt.  The bane of all audiophiles known to take down even the high and mighty.

I agree that the XA-30.5 may not be the perfect amp for those PSB speakers. However, there are other factors at play. Pass Labs gear tends to be warm and musical, so combining a Pass preamp with a Pass amp may be too much warmth and not enough detail.
Many Pass amp owners use an ARC preamp, like myself. The ARC provides a bit of speed and resolution to the musicality of the Pass amp.

That said, I'm still not sure that the XA-30.5 is enough power to drive your speakers. My room is 24 (L) X 15 (W) X 9 (H), my speakers (90 dB, 5 ohms) are a bit more efficient than yours ( 88 dB, 4 ohms), and I am running XA-100.5's, which provide plenty of power. 
If you seek greater liveliness, it could be an amp/speaker mismatch, in which case I would change the speakers, or it could be that you need a preamp with a little bit more life.