Jojo's tip:
The best approach in upgrading "any audio electronics" is to study the circuit, learn how it works, why it sounds like that, which part or parts dictates sonics. Gentlemen (any ladies?), the best weapon in this hobby is knowledge.
Common practice of diyers here is to change opamps, caps, bypass caps etc, and then you end up changing everything. Some websites even change the main supply caps because "1000uf lang?!? eh" let's change it to 4,700uf. Then what? Do you gain anything? Have you even considered the PSRR? Refining ripple won't give you any improvement if the PSRR is way beyond specs. That just won't cut it.
As an example, take an opamp specifically designed for audio then use it and exploit it, push it to it's limits, squeeze the darn thing until it sounds good, find the best possible configuration for it to sound it's best. Remember, an opamp works because of resistance in it's feedback, without it, an opamp behaves like a piece of wire with a gain of 1! Too much of it and you approach it's open loop gain and you lose bandwidth.
Study how the circuit works and exploit it!
HTH,
JojoD
