It all depends on who is doing the modding and what their track record is. Modwright and Backert Labs both started modifying electronics. Perhaps people have heard of them? Ric at EVS mods mostly digital equipment. I'm sure there are others. You just have to use due diligence in your search.
I would not dismiss them out of hand. However, as @tablejockey pointed out, the PL gear is already full of premium parts. Not sure what you would gain with mods?
If you have money that is burning a hole in your pocket, why not check out some of the newest cheap class D amps. You may be surprised.