Mixing or matching component brands

Over the course of many years I have put together systems both comprised of mixed and matched components.  Sonically it can be acceptable either way.  Aesthetically matched component systems are more appealing to me.  Brands have varied, but were chosen always because the dealer that I chose carried it and recommended it.  Since buying my first system in 1963(?)(or 1962) I picked the dealer first.  When I was in college I worked for a dealer who carried both McIntosh and Marantz so of course I tried both buying on accommodation.  After college I worked for a dealer carrying Audio Research so I tried that brand.  Today I have two systems in different locations, one is all Conrad Johnson and the other all Marantz.  

mix match the best stuff is the best way to get optimum performance. pigeon-holing yourself makes no sense.

Went with current gear cos they allowed me to optimise my listening and room/speaker marriage

Decades ago there was no way to put together a high end system without mixing. Threshold (Pass 1980) made the best amps, Audio Research made the best preamps... including a phonostage back then. There were other budding brands... some, pretty disappointing, a few with a single good type of component. 

So over time these specialty companies increased their engineering expertise and established house sounds. So, now you have the Audio Research sound, Boulder, Burmeister, Linn, MacIntosh, dCS...etc. Each component complimentary and of equal sonic quality. 

There are still differences. My opinion is that Pass still produces better amps, than they do preamps. Their amps continue to improve. Over the last ten years the rhythm and pace has improved across their amps. 

So, if you have the money to buy a top tier that matches your desire for sonic characteristics you will be very rewarded for getting all Audio Research (what I have now), Conrad Johnson, Boulder, Linn, Burmeister... etc. They will be voiced the same way and synergistic. Best case scenario. Then you can connect them with the most transparent wires. 

If you cannot afford this, then you may end up mixing and matching. A tremendously more complex task. The interactions of different sound types makes for a nearly infinite number of combinations. But, if you are good with very complex ambiguous problems, you can do it. It can be fun. Some folks are simply not up to the task and will constantly be let down by their choices, I know some folks like this. They should audition systems and buy the one who’s house sound appeal to them the most., 

I've achieved good results both ways. If you can pair high level components from the same brand there is less worry. Same brand amps and preamps should be built to match, and be a natural fit. There is no reason you can't get great results mixing brands if you take care to study the specs, and make sure their tuning is compatible.