If your preaqmp has 2 oputputs, run one to the fulrange amp and the other to the sub. That way, there is no risk to the full range signal. This of course, assumes your satellites can handle full range sound well. This will work best if your preamp outs are buffered from each other. This means the 2 outputs are electrically isolated form each other. I have a similar situation, running Entec subwoofers and a Behringer EQ from 1 output, and full range speakers from the others. My outputs are not buffered from each other, so if I make changes to the EQ, it affects the sound of the main speakers. I think only the volume of the sound changes, not the fundamental character of the sound, but it is worrisome to me nonetheless. But the system sounds good, so I won't get too worked up over it. The only way I know of to tell if the outputs are buffered from each other is to call the manufacturer and ask.
What subs are you using? Maybe someone else here has them and can answer more specifically.
Re: your question, the signal will certaqinly pass thru the subs crossover, which could cause degradation. The more complicatred the high-pass portion of th crossover, the more likely there will be degradation. There may be some line-level preamp type gain stages involved, particularly if the sub allows you to do any processing of the high pass signal, such as boosting it's level, changing phase, whatever. I think most subs, though, have this type of control working on the bass, not the rest of the signal.
What subs are you using? Maybe someone else here has them and can answer more specifically.
Re: your question, the signal will certaqinly pass thru the subs crossover, which could cause degradation. The more complicatred the high-pass portion of th crossover, the more likely there will be degradation. There may be some line-level preamp type gain stages involved, particularly if the sub allows you to do any processing of the high pass signal, such as boosting it's level, changing phase, whatever. I think most subs, though, have this type of control working on the bass, not the rest of the signal.