Sorry for the delay in my response. My cross-over (that I'm not using) supports the center channel and rear remote volume features.

My amps (old rockford punch kidney bean amps, 60ix and 4040) have internal cross-overs. The 4040 (20x4) has 2 crossovers for the "front" and "rear" channels in addition to a crossover for the combined output rcas. They run to my punch 60ix for the subs.

I've got some wild ideas on using the "rear" 2 channel of the 4040 so acheive my rear fill and center channel speakers. Use one of the sides (left or right, doesn't matter) and patch it to the "center" channel output of the crossover then use the rear rca's, mono them together and run them from the other channel. The other pair remains your front stereo speakers.

Since I'm in a jeep wrangler, this is all full blown overkill to begin with, much less adding the crossover and center channel speakers to go with a car stereo with 9000+ tunes.