Find new music to listen to. From my own perspective I listen to a lot of shit stuff these days, but it is different and is new You think that you have tweaked your system to the nth degree and therefore the tons of cables (well I have) that you think haven't nade the grade are up for a swappsises session and they may surprise you.

If you have several pre-amps, amps, dacs. speakers etc etc - substitute one or more and see how the system sounds. You have to listen to music to make an assessment and so the system is getting used.

Don't have a subwoofer? - Get one. The difference that these can make is immense. You don't have to try to demolish the house foundations with one (or two or three - I have five) but only use one at the moment. Play with the phase it will surprise you.

If you're speakers are bi-wireable try changing the phase of the bass or HF again the results can be very interesting.

If none of the above takes your fancy then just get bladdered and turn the system up to 11.