again on 6-24 cross

Hello, everyone,
I'd like to know if anyone has used the 6-24 crossover pass to enter with a stereo signal and exit with frequencies above 100 Hz still with a stereo signal and with frequencies below 100 Hz with a mono signal going to the subwoofer amp. Use the 6-24 to sum the left and right channels and output in mono without losing audio quality.
Thanks in advance to everyone for any suggestions.
Cheers
Giubos