I think you are mis-understanding my post. There is no "pride" associated with tearing out anything. We take pride in satisfying our clients. I know that sounds cliche but it's truly what we think about everyday.
Everything you want to do can be done
for a price. I would find a good Residential Integrator in the area and have them develop a system design and budget.
Control4 has some good solutions for use cases like this. Take a look at their blog, as well.
The audio down-mixing happens on the input side so that it knows what format to output to each device. If it happened on the output side, you wouldn't be able to "mix" audio outputs on a card. I suspect it is more cost effective to do it on the input side.
The new card is more expensive but not terribly that much more. I am pretty sure it supports all of the major advanced audio components but I haven't looked at it that closely. It is a 4 port card and you can mix and match it with the other cards.
Here's the link to the card on their web site.
I don't know that there are many switches out there that support 4K yet. It is still very much an emerging standard.
Unfortunately, the C4 matrix is not PoE. That's the one big drawback of it. That being said, it's a great price point for a good product.
The audio issue is a known issue with savant. It's the reason they just came out with their new DSP cards. Before the new cards, if you has a source like AppleTV distributed to both surround zones and stereo zones, you had to set the audio to PCM as it wouldn't work in stereo zones if in Dolby. With the new cards, that issue goes away.