Comparisons between Pass Labs and Pass/Threshold

Can anyone offer listening comparisons between any of the new Pass Lab amplifiers and the older Pass-designed Threshold equipment? I presently own both the Pass/Threshold S300 and the S550e, the former purchased new and the latter purchased used/mint. Those are the two older Pass amps I know best. Do they have close counterparts in Pass Labs amps? Is it worth trading up? Those are the kinds of questions I am most interested in. Thanks much.
Those are great comments. The nearest Pass Labs dealer is a 3.5 hour drive (even with troopers snoozing), so auditioning is not routine. My associated equipment consists of B & W 801 Series II speakers, Threshold Fet 10 Preamp, and Sony SCD 777ES CD player. My continuing enjoyment of the latter has, for the time being, reduced use of the VPI Mark III TT with Audioquest PT6 and Blue Point special. I moved to the S550e from the S300. I have retained the S300 for alternate use or possible trading. I am a satisfied customer of Nelson Pass designs. Based on my experience, he is a dedicated designer and manufacturer of solid, high-quality equipment. The next Pass step, I suspect, would be to audition the X series.
steve,you mentioned the amp is 30 wpc.Are you sure you meant the O's and not the aleph-3?
David - Good catch! Don't know what I was thinking... Thanks...

The amp was definitely the 0s and it puts out 40 watts per channel...

JDH9 - Looks like you have a nice system! Pack a good lunch for the drive!!!! It'll be well worth it!!!! I'd be very interested in hearing what you think about the X stuff... My nearest dealer is ~2 hours away and that's also why I've yet to hear them....

I can vouch for the Pass 0s. It blew away any solid state amp I compared it to. I heard friends jaws hitting the floor when my Martin Logan Quest's started playing. I would set them up by telling them it was "only" a 40 watt amp. Other amps that I also have enjoyed are a Plinius SA-100 MKIII and an ARC 100.2 both at 100 watts per channel. Since I own a pair of Coincident Partial Eclipse speakers, I can drive them with an AES DJH Superamp and have not even considered solid state. Good luck finding a match for your speakers.
All of this makes me think I should find a way to hear the Pass Os. Thanks much.