Quandary

I think that the $300 review, which involves two trips by the dealer, plus the opportunity to have the $300 put toward the purchase price is a reasonable offer.  Whatever you decide, it is a decision informed by much more than most people base their decision on--you got to hear the amp in your own system, at your leisure.  

@rvpiano I am not sure how many power amplifiers you have owned, but the difference in presentation between the Benchmark and the Pass are quite different from each other, and would be, with any speaker. My advice to you, is to take your time, breathe easy, and play many pieces of music you recently enjoyed with you Benchmark, and allow the Pass to do their things. "Relax" during this weekend and ENJOY ! You will know which is more "engaging", as this is a term I talk about a lot. Do not think too much about it, and simply, listen. I will continue following this thread, so anything you want to discuss or comment on with all of us here, we have your back. Remember, you are trying to satisfy you...not me, not anyone else....just you. My best, MrD.

The only caveat is that I won’t be hearing the exact same thing that I’m buying. 

yes, that's a big caveat

Right now the Pass seems a little “overwhelming” and not quite as detailed as the Benchmark on some things. I have to keep the volume knob way down. However it certainly fills in a lot of gaps in volume that the Benchmark lacks.
I suppose that was to be expected.  

OK, the $300 is invested.

If you would decide to go ahead with purchasing the Pass amp maybe (if you haven't already) it's a good time to discuss in the unlikely event that you feel the single chassis Pass is not a significant enough improvement to warrant the expense, the method that this would be handled.

  LP