Is there any merit to assembling a same stack system to achieve excellent performance?

There can be. Things like impedance matching for example should be a non-issue with items from the same manufacturer, and "voicing" should be the same. I had a pretty nice system that consisted of a hodge-podge of brands. It got a lot better when I went with a combination of Herron monoblocks, preamp, and phono stage. I certainly might be able to change out one of those items with something "better" from another manufacturer and have more pleasing results.

This is one of the reasons some people prefer integrated amplifiers to separate amps/preamps.

Having a stack of the same brand should take any guesswork about how well the components will match up out of the equation.

A lot of what audiophiles think of as settled and proven turns out to be bunk. System matching is one of the more frequently misunderstood. When you go looking for a component it should be with a clean slate. Unfortunately sometimes you may find yourself painted into a corner. Like you forgot speakers need to be 92dB at least, so you bought some hard to drive 87dB power hogs, and now need to find an amp capable of driving them. Do yourself a favor, don't be that guy. Do yourself another favor, don't call this "system matching". Call it what it is, slapping a band-aid on a self-inflicted wound.

When it comes to speakers, eliminate from contention all that are under 92dB. Just do it, and thank me later. Then from whatever is left choose according to listener evaluations of how they sound. Do the same with everything else- first filter out the stuff that you know will limit future options, then select the best from whatever remains based on how it sounds. Not measures. Sounds.

If starting from scratch, first decide if you are looking for one and done (a complete system never to be upgraded) or if instead you are looking to get started on a system you hope to grow and evolve over the years. Because budgeting is different depending on how you answer this one very important question.

Too simplistic? Hardly, if you like the manufacturers house sound. Instead of trying to cobble an entry level headphone system together I decided on a Schiit stack (including cables). Made sense to me and wasn't disappointed.