Adding a Sub can improve the overall sound, but only you can judge whether the investment was worthwhile or not.

You have the usual benefits from adding a Sub; the Sub takes care of the bass whilst allowing the Fives to concentrate on mids and highs.

If you listen to bass-heavy music and at higher volumes then the addition of a Sub will be more noticeable.

I’d actually look at a new or certified refurbished Sub (Gen3) rather than Sub 4, potentially saving £100-£200, or even a Sub Mini.

I absolutely loved that set up when I had it.  The sub frees the Fives from the low frequency stuff sound better.  Then there is the extra bass 😍

You can try one on 100 day trial.  I doubt it will be returned!

One thing I found is that Trueplay made a big difference so if you don’t have an iOS device I’d borrow one to do a tune.

I think the returns period has reduced to 30 days, but that’s still plenty of time to decide how much you like the addition to your system 😜