I have M3s, a 150 centre, and QS4 surrounds that are a bit over 20 years old. Should any of the crossovers be replaced or upgraded? Is this a thing, and how would you even know if the speakers are all working?

Thanks,
Apologize if this have been asked before

I guess if they still sound good, why mess with a good thing? I still have many of the early versions of Axiom speakers, as well as stuff I had back in the 80s (aka Pioneer 4way speakers, receivers, tape decks, etc. All still sound dang good when I dust them off and crankem up.

20 years is an eternity for consumer electronics. The interconnects and power delivery of my devices weren't even invented yet in 2003.

That said, a good 2003 loudspeaker is still a good 2023 loudspeaker. I'm in favor of granting amnesty to legacy sunk costs as long as it still serves the needs of today.

You can open up the loudspeaker and checking the crossover circuitry for any capacitor leaks or swelling. I don't think it'll be an issue for another decade or two.

Your M3s would benefit from a tweeter and crossover upgrade. Alternatively, you can trade the M3 for M3v4. You will enjoy a wider, deeper and more satisfying soundstage and imaging.

Compared to the 160v4, your 150 is total garbage. Trade that in for sure.

QS4 are crap compared to QS10. Trade.