OP
mixing and matching is, in my humble opinion, the audio Synergy that one individual is searching for the ultimate configuration in one's Audio journey. It is Fun and $$$.
My take is, all manufacturers (the good ones) build their gear to synergies to each other, BUT that is their opinion and hearing. As an example, I heard a complete Mcintosh gear and I would say, they sound wonderful. However, for Me, my gear synergy is a level above the Mac setup I heard. As far as the $ amount, I am comparing close to apples to apples. I also would like to say Not all manufacturers are an expert in building all audio gears. some may be good at building amps, other speakers, etc. The only reason why one would like to go to a one manufacturer is that its a one package deal, one trust the quality and synergy of the company, easy on the support and just not that willing to undertake the audio journey. I have met a few acquaintances' who had an all-Mac gear, all PS audio and some have an all-BOSE gear (ha-ha).and said to me, they just want an all-in-one package. When they heard my setup, we all agreed that my setup is a level up, but they all did not want to undergo the years of me continually changing gear. plus the fact that the better half may not like the looks of not matching gear
In the end, I am a firm believer that mix, and matching gear is the ultimate solution. another player is your budget $$$, compromises are settled here. Mixing and Matching gear tailors the sound to YOU, the listener.