James
Lord of the Erg\o/s
If the OP doesn't want to add a resistor to the HP filter, I don't think he'll entertain this suggestion - even if I think this is the primary answer to the question.... but the crossover would have be changed if you wanted to add them to an existing speaker, including the mid driver's low pass section.
How about a parametric equaliser? The OP can then selectively dial out the annoying peaks. Oh wait, he does not want tone controls either.
New loudspeakers then ...