Using an 80 Hz crossover is the recommended setting, but if 100 hz sounds better to you, its easy to change in the AVR, so you could try both and just keep whichever sound better to your ears. 80 Hz and below is considered 'omnidirectional' to human perception, meaning you will not be able to discern the origin location of sound in that range. That is good for subwoofers since it means the subs will not draw attention to themselves and will be able to blend in better with the speakers for a seamless sound. Above 80 Hz, the sub may be more localizable, and weigh the soundstage in its direction, obviously not a desirable trait.