Hi

I don't know what you may be refering to, but I think this has something to do with equipment's maxium input/output level. If your crossover's input level is capable of receiving +15dbu signal from the pre-amp without clipping then you probably will be able to boost few more gain at crossover stage to hit even harder to the amp stage if it is capable of that high headroom. As long as the amp or crossover don't overload and the gain is set reasonable then I think attenuation won't be necessary.

I used to have a dynamic compressor to limit those signal peak, but found it actually screw the sound alot and eventually end with just lowering the gain instead. It actually sounds better. Just from my experience