Ideally all RAM would be of the same make and speed. The further you get from the ideal the more likely problems become. I say "more likely", but in real life, you could have every stick from a different maker and still have no problems (I see computers coming in for repair like that--they're being repaired for viruses or dog fur, not RAM issues).

But me, I like all my RAM to match.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs