Raspberry4, audio e PeppyMeter

hi everyone, I would like to increase the quality of my listening system, on speakers, no headphones, by switching to raspberry4, unfortunately my current board is not compatible with rpi4 and I have to take another one, which is also compatible with PeppyMeter, perhaps with toslink digital output rather than rca, what can you recommend?
Thank you…

Digital RCA connection itself is far better than toslink.