well,
keep your center and fronts from the same brand, the same range (series), and if possible, the right match.
the rears can be changed, but, this is not recommended, same rule as the fronts in fact, but a little less strict,
the sub on the other hand, can be from a different brand, just make sure it matches with your speakers (in power and size and stuff) if you have huge speakers, don't buy a tiny sub, and when you have small speakers, don't buy the huuge sub, well, you can, but you'll never use it in full operation.

Greetings,
Basite.