If you low pass your mains at 80 hz, this could be a less expensive alternative to see where your at. You really do not want to cross high and low at the same 80 hz frequency. A bit higher [high pass cutoff] is recommended rather than the same as the low pass filter cut.
http://www.parts-express.com/harrison-labs-fmod-inline-crossover-pair-100-hz-high-pass-rca--266-274
http://www.parts-express.com/harrison-labs-fmod-inline-crossover-pair-100-hz-high-pass-rca--266-274