Quandary

The only problem is he doesn’t have the 30 watt amp in stock but would have to demo the Pass sound with 60 watt monoblocks.

For $300, dealer should at least let you listen to the amp in question.

When I had my Triton Ones, I used an Odyssey Stratos amp which at 150wpc and 60 amps of current was a perfect match to the Triton Ones. I moved on to the Triton Refs and now use a 300wpc McIntosh amp which puts me over the moon

Excellent point. Pass will be better but so could a lot of other amps. If you are on the amp upgrade path, are you willing to "settle" for the first one you hear.

If it was me, I would question how the Pass will blend with the Triton's digital bass amps.

It’s telling that you were satisfied with your system, and he made the suggestion of an audition, not you. My dealer would never charge a fee for me to hear a component that he is trying to sell. Even if you can get by that, you are still not going to know after the audition because it’s not the same component.  You might get some approximation of the pass house sound but the component you’re going to audition will likely sound very different in your system than what he is actually trying to sell you. At a minimum, I would insist that you audition the particular component that is under consideration. 

@OP -  you should find a dealer who will allow you a home audition of the amp for free. Offering to waive the $300 cost if you purchase is a clever sales tactic to subtly pressure you into buying in order to recoup your $300 outlay. In addition, it's ridiculous that he wants to charge to demo an amp which is not the actual model you would be buying. The Pass class A amps have a common sound character but they don't sound identical. However, as regards the comparisons , if you find your Benchmark slightly sterile/mechanical sounding, you will love the Pass. But you would need to hear exactly what you would be contemplating buying. The amps sound good from cold take an hour to warm up and about two hours to sound at their absolute best.

This sounds similar to a senior phone scam. 

About the Pass 30.8: Why not buy it here, used, for $4500 and resell it if you don't like it? The amp is $7.2k new, so you won't lose very much on resale, especially if you bargain a little.