Thank you for the explanation!If you look at the D.C. Levels at those caps then add the max voltage swing.
For input probably not more than +/-2v plus 1.5vdc so a 5v could theoretically work. For output D.C. is about 7v. Max output swing is about +/-5v so 12v would be minimum for output. But for lower distortion you don't want to have a cap too close to limit. I use 35v Elna Silmic and film cap is 50v rated.
If I want to roll caps in my other devices, would measuring the positive leg of a cap relative to ground give me a good idea of what voltage rating I need?