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

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.

I've gone for synergy with a system of mainly Linn Products components. 

I started out with a more eclectic system, but this is the way it's evolved over the past 25 years.  

Mix and match for best sound:

Preamp:  Rogue Audio tube

Power Amps: Odyssey Audio SS mono blocs

DAC: Schiit Gungnir2

Streamer: Innuous 

speakers: Fyne 

Cables:

  Speaker: Silversmith Fidelium

  ICs: Fidelium XLR, Groneberg and Morrow RCA

  Digital: Pine Tree Audio & Audioquest

   Power: Ice Age Audio & Audioquest

It was a little bit of trial and error on the power amps and cables, but what I have now is yielding superb results.

The OP is a dealer for Infigo and should make this disclaimer on every post. New people here every day and this is unethical.

That being said I mix my electronics to suit me never found a house sound I like. With cables I use all the same brand for IC and Speakers, Purist Audio Designs, Digital (USB and Ethernet Clock)) Final Touch Audio, Power LessLoss, C-Marc Classic. tone arm wire is Cardas. 

Mixing different brands doesn't matter.  Sure, there are situations where there might be some issue, but for the most part, no.  I remember years ago, a Linn/Naim rep visiting a local dealer told me it was never a good idea to run a wide bandwidth preamp into, I guess, a narrow or narrower bandwidth amplifier; some instability issue, I recall.  Yet the dealer ran a Spectral ultra-wideband preamp(into the meagahertz) into an Audio Research tube amplifier with spectacular results.