Harrison Laboratories

I'm considering using the line-level high pass crossovers available from Harrison Laboratories. They will take some of the load off my main amplifiers and letting a dedicated subwoofer take more of the burden, say below 70 Hz. I'm pretty sure they are 12dB/octave devices. Does anyone have experience with these little gadgets?
I have used the attenuators they make with good results.You can also use two for a 24db slope! Parts express sells them and they give full refund if they don't work out!
I have used their attenuators also. Know nothing about the crossovers but would expect a good quality product that performs as advertised.