Mr. Tennis,
You're cordially invited to join me on a hifi adventure. Please take a trip with me to a number of manufacturers so that you can see how many different models of speakers an average hifi amplifier manufacturer owns or borrows to test his or her equipment. Or, how many different types of amplifiers that an average high-end loudspeaker manufacturer uses to design, develop, and test their speakers.
How much money do you really think they budget to spend on other people's gear for the sake of testing and exploring compatibilities?
I promise you enlightenment on this journey as, in my opinion, coming from someone who has already taken it, your faith is misplaced.
Manufacturers know about THEIR products and to this point I do not argue. However, when you start talking about how their product will perform within a system comprised of many products, or with another manufacturer's product, or in a specific room, or with a new control system, then they will most likely only reference the specs and make assumptions regarding engineering compatibility and not sonic compatibility. The two are not the same and I'm sure you realize this.
And, I'll be the first to admit if I don't know what to expect by pairing brand X with brand Y if I have never done so.
As a dealer that some manufacturers have turned to for beta-testing, I can tell you that most products are finalized in the field and dealers provide a considerable amount of field testing and data. When problems develop, manufacturers often turn to their dealers and integrators for suggestions and solutions.
So you see, it's not a one or the other type scenario. The relationship between manufacturer and dealer is symbiotic.
And, as such, I would recommend involving both. What's the harm in doing so?
Best,
Burt