Wondering why you are looking into this? Is the audio amp chip bad in your R20?
Just wondering as I can't recall reading anything about a problem with the R20 audio circuit.
Oh I see!
Well, bumping the output from the existing audio amp is probably not wise although achievable, if tricky. Personally I would suggest going for an external speaker/amp; lots of the usual sorts of Bluetooth speakers have an audio input socket and this would be by far the safest and easiest way of getting more audio output when you need it.