Nope. Not quite what I’m sayin.
I will speak only for myself(although I believe others feel similar).
IMO you can usually upgrade within a manufacturers stable, but not a different brands. For example, SVS voiced the prime and ultra lines intentionally to be mixed and matched. That way if your budget forces a compromise you can choose how to allocate it. I believe many companies do this. You wouldn’t however want to have Revel mains with a golden ear center, or klipsch mains and a Polk center. They’re just voiced differently. Maybe a Revel/jbl combo(just an arbitrary example) since they’re both in the Harmon stable and probably sound more similar than not.
I have had a couple Frankenstein systems in the last 30 or so years(I’m43), so I feel qualified to say IF you can invest in a matching speaker system, there is no reason not to. You can get decent performance from a mix n match from different brands, and some will say it doesn’t even matter, but I totally disagree. Especially if your spending good money, why not? Even if you have to squirrel it away for awhile.