Matching Gear matter to you?

you have no idea what will sound better to you, the only way is to try and pick the best combination no short cuts.  overall you won't go wrong either way but the same brand's set could sound better and than you lose nothing except some money. my preamp looks like something portable and it's silver and made 30 years after the power amp which is black and much larger like most home components, so what? the modded look gets more respect and it's good for the ego to match components not from the same brand so you can brag on audio forums about your matching skills !

@verdantaudio its all single ended.

As long as the piece of equipment being considered can handle (load, impedance matching, etc.) the other equipment, there shouldn't be an issue.

Then, it comes down to how it sounds in your system.  First, most companies don't make everything anyway.  Music servers, streamers, DACs, turntables, Speakers, cables, etc. so, there will be a slight mix anyway.

Also, just because a company makes say, amps, preamps and DACs, doesn't mean that they will be the best for the money you plan on spending.

so, it comes down to auditioning in your home and in your system.  If a dealer thinks you are a serious potential buyer (maybe spend quality time with dealers helps),  they will take your credit card information and loan you a piece (typically demonstration unit) for a few days.  

That has been my experience.  Also, there might not be many dealers in your area that have variety.  Sometimes they are stuck with only a few  manufacturers in house.  This limits your direct listening ability and comparison opportunities.

Sort of the Bose experience.  Bose makes it so you really can't compare directly their stuff with anyone else's in stores.

enjoy

Surely the important thing here is output and input impedances, and this is going to come into play most acutely between the preamp and amp.  Although a great many do, not *all* preamps and amps work well together, causing premature rolloff (p.r., an acoustic affliction) and other nasties.

then it comes down to what defines "better."  Synergies between products are very real.  Few other things to think of:

Does the off brand product have the right level of gain to match with your amp?  Preamps can have wildly different levels of gain and the appropriate amount is dictated by the amp.  Most companies preams will compliment the amps in the same line. 

What is the tube compliment?  Sometimes one product is better with stock tubes but when you roll in different tubes, another can excel.  In some cases, you have virtually no choice in what tubes you get. 

What sound profile are your trying to achieve?  There are a few companies that I can think of that produce tube preamps that sound solid state.  Does the off brand component serve as a substitute in terms of sound profile?  

One persons "better" is not another persons.  Are you sure that this other preamp is better?  Is there a technical reason why?  

Incidentally, doesn't matter if you answer these questions here.  Just want to provoke thinking to make sure that you are making the right choice.  Years ago, I bought a power amp not really knowing how finicky it was with preamp pairing.  I demo'd four preamps (amp in tow) to get one that sounded great.  Saved myself $1000 vs just going with the preamp from that brand and have no regrets about it.