If you have Audyssey turned off, that is ok to reduce the crossover setting, however, you only want to increase the number with Audyssey engaged. Otherwise, you are losing material between what you reduced it to, and Audyssey's results.
I am not sure what you mean by "losing material". I think you will find that when you lower the crossover from what Audyssey suggested that you do not have Audyssey processing in that channel for the frequency range that is below the crossover that Audyssey calculated.
