Clayton M300's vs Pass XA 100.5

I'm considering these two fine units. Besides the difference in power, might anyone have insight into comparative sound quality of these two full class A amplifiers. I plan to use a VAC Ren mkII to drive either in balanced mode. Also if anyone has insight into how the Claytons squeeze 300/600 WPC into 8/4, vs the Pass Units, I would be greatful.

I was considering Clayton and Pass Labs a year ago. Clayton amps were
impossible to audition, and there was a dearth of dealers, none of whom had
product in-house.

On the other hand, Pass Labs amps were easy to audition in my home, and
service was clearly never going to be a question.

I would have liked to give heavier consideration to Clayton Audio, but I got
the impression it was a super small, boutique company with limited resources
and support.

I chose Pass Labs on the strength of the company and dealer network.
I agree with all above,however that said, Go with the Clayton. It's a great amp. I've owned a few Pass amps amd while they are great! I'd go for the Claytons. Claytons have a way of doing it all. With Pass you have to pick which amp will work the best. Say, X350.5,X250,and XA100.5. The Pass amps I just mentioned are the sweet spots of each serious. If you can figure which Pass amp will match with your speakers,then the Pass may work well but, Pass amps (IMHO) tend to be very speaker dependent and preamp dependent as well. They need a lot of push but, if matched correctly can be heavenly.
Audiobrian I would have to agree with Tvad's points made. I was also very interested in the product but ran into the same situation and my thoughts mirrored his, I got Pass X600.5 mono blocks.

In the past I have run into issues dealing with such super small, boutique companies such as Supratek and lastly Cat all with bad experiences.

If the product is readily available to you, the dealer is supportive and you feel if there are any issues what so ever you will be looked after then I would suggest try them, suppose to be really good product.