The power supplies are external and easily swapped. However if you want to try alternative resistors, caps, and internal wire, de-soldering the original pieces from the PCB is a PITA. Consider researching substitutes for the initial build. The schematics identify the necessary values. I used Welwyn RC55Y resistors in the 1/4W positions(excellent at @$2), an Audio Note Kaisei electrolytic in the large coupling cap position(in parallel with the largest film cap that would fit across the top of the Kaisei), a 4.7uf ClarityCap film cap in place of the small electrolytic at input of signal path, and Panasonic FM or FC electrolytics in the power filtering positions. The point-to-point wiring can be whatever you like.
No, I have not heard the amp equipped with stock piece parts.
These mods add a few hundred bucks to the build.
BTW, these amps have relatively low gain. A preamp with gain may be appropriate when matched with less sensitive speakers.