Maybe $25,000 ? jk Primarily the transformers. Stellaris has custom nickel windings (I believe), while SSpecial has silver secondary windings on the Output transformer. SSilver is all silver windings, both Input and Output transformers, plus silver wiring & silver dueland foil caps. And Specials have speaker outputs of course. Now, I have never heard or even seen the SSilver, but it is whispered that at least one now exists in the wild... Saving my pennies.