I had to look up passive horizontal as I was not familiar with the term. One source said it was often referred to as "fool's" bi-amping.
In light of what you say and what I gleaned from quick research, probably best to leave as is. My preamp has both high and low bass management. I currently have it set at 60hz so the amps in the subs are handling the low end and my other two can loaf along with stuff above 60 or so.
I'll continue to arbitrarily switch them to keep the juices flowing so things don't dry out. Thanks for the info.