Waxing a garbage truck?
You don't mod PVs to sound much better.
You start with an amp worth modding.
And that would be a tube amp. Not transistor.
The most obvious thing is the speaker. The speakers in PVs don't sound any good.
But installing a $150 speaker in a $50 amp is beyond what most people would do.
No, I would not spend the money on capacitors, unless the caps are actually bad.
But what I would do, is fix it and sell it.
Then take that money and buy a tube amp.