Do you use one brand of electronics or are you mixing brands what has worked best for you?

I mix and match, though all of my new tube gear is all Aric Audio

I use the same main electronics - but only because of their quality and value for their time and the fact that the manufacturer used the best designers of their time for the individual components.  I use the (old) Aragon 4004 mkII designed by Dan D'Agostino (Krell) a dual mono 200WPC (800wpc @ 2 ohms). 24k a fully symmetrical, component level pre-amp with MM or MC phono stage, outboard PS and the discrete component tuner designed by Magnum Dynalab.  The industrial design of each component is unique and they are in the Smithsonian as an example of industrial design. 

These two attitudes are valid simultaneously in my opinion according to the acoustics circonstances ( Acoustics with an "S" here mean psycho-acoustics not just room acoustic)..

The problem with the words "neutral" "warm" "cold" is they are adjectives used by subject focusing on gear pieces synergy.

There is no concept of neutral warm or cold in psychoacoustics parameters...

These concepts though being subjective descriptors correlate with :

«

• Warm Sound: Generally associated with an emphasis on lower frequencies and lower-midrange. It often involves:
  • Rolled-off high frequencies (darker sound).
  • Softer transients.
  • Even-order harmonic distortion (often associated with vacuum tube amplifiers).
• Cold Sound: Typically associated with an emphasis on higher frequencies (brighter or more "brilliant" sound). It often involves:
  • Scooped midrange.
  • Sharper, more pronounced transients.
  • Odd-order harmonic distortion (sometimes associated with early solid-state electronics). »

But doing so  condition us to put attention only to half of our acoustic experience related to the gear pieces synergy out of any psycho-acoustics and physical acoustics context (room) ...Then Neutral position is not enough, nor warm and cold  qualifications.Read me right: i used these two orientations of  our two friends poster myself, but it is not enough and it may become misleading, taking attention from the system/ears-head/room toward gear synergy which is merely a starting point...

Then i also search for a "neutral" balance between "warm" and cold" but this is secondary concepts, i try to understand how ti implement natural and realist "timbre" experience through my system/room first and last and i try to optimize the acoustics spatial cues various dimensions.

My unprovable theory is that if you find a house sound that is perfect for you. All the same components should outperform mix and match. I cannot prove it. But to me, each component must be subtractive in some way. Say your first component is lean, and the second really warm, and third lean, and amp is warm... aren’t you loosing nuance at each component when they are of different character. I will not defend this. It is just a thought experiment. 

@ghdprentice  Very adventurous thought process — I like it. To add to that, my view is that any coloration (anything non-neutral) acts like a filter that accumulates or cancels out across the entire signal chain (cables included), ultimately altering the system’s frequency response. So to minimize that effect, it’s preferable to keep components as neutral as possible and preserve that neutrality until the very end of the chain, where you can make intentional adjustments to the timbre or overall tonal balance for better coherence.  This principle could be duly applicable to a mixed and match system as well.

I just used warm and lean as examples to demonstrate the concept.

At times (including now), I've had the same-brand preamp and amps, and I think that's desirable.  I also have the same-brand DAC and DDC, which is also probably a good thing.  Otherwise, it's mix and match.  Even with three different Nakamichi cassette deck models made around the same time, a cassette sounds different played in each one, so using the same brand doesn't guarantee compatibility.