More than just amplifiers, it's also the finishing process used in guitars. That's why most manufacturers don't use nitrocellulose lacquer anymore; it's nasty, dangerous stuff that's hazardous and environmentally sensitive. So now, most all the guitar manufacturers use polyurethane.
And in the case of Behringer, I think Peavey is right to sue them. Their subsidiary company, Bugera, makes budget-oriented amps that are based on other company's designs. They take another company's design, reverse-engineer it and make a few cosmetic changes, and release it as their own. Their 333 amp is a direct ripoff of the Peavey JSX, right down to the design of the faceplate. They've also copied Mesa/Boogie, Matchless, and Marshall.
Most acoustic luthiers of high-end guitars still use nitrocellulose lacquer. The big exception is Taylor Guitars. Using nitrocellulose lacquer would be too expensive for Bob Taylor because of California's state EPA regulations, so he uses a catalyzed polymer finish. Martin uses a rub-on poly on a few of its entry level guitars, and NCL on the rest of its line. Gibson uses NCL on its acoustics.
The catalyzed polymer is a harder finish that can be sanded the same day it's sprayed, so some smaller luthiers are using it now.
Electric guitars are another matter, because the finish isn't as important to the sound 'purists'. Fender (in California) actually started its production in Mexico so it could spray NCL. It would build guitars in California and run them through Mexico simply for NCL finishing. Now, it makes entire lines of its guitars in Mexico.