+1 to Metralla's comment.
Vance, I'm not certain that the Classe person you spoke to was giving you a precise answer. Breaking capacity (also referred to as "interrupting rating") has nothing to do with the likelihood that inrush current at turn-on will cause unnecessary fuse blows. Or, at least, there is no direct relation between the two.
Breaking capacity refers to the maximum amount of current occurring under fault conditions, when the fuse SHOULD blow, that the fuse can deal with without an explosion or other safety hazard occurring. That rating will be far greater than the current rating of the fuse.
The parameter that is most relevant to withstanding inrush current without blowing unnecessarily is what is called the "nominal melting" point of the fuse, which is usually specified as (amps squared) x (seconds).
Datasheets at the Littelfuse site provide very comprehensive technical data on their fuses. You might want to look up the specs for the particular fuse that is in your amplifier, and ask the manufacturer of the upgraded fuse you are considering if they can provide you with the nominal melting spec for their fuse (as well as its breaking capacity, which as I said is relevant to safety). Their response should be interesting.
Regards,
-- Al
