Hi Kid, it does add more punch or impact, especially if you have an amp on the horns with a gain control. Biamping alone seemed to help but bringing the horns volume down slightly to give a more balanced presentation really made them hammer. It makes them give you more of a hit in the chest feel.

Your Fisher receiver would be a cool set up if it had preamp outputs. The Fisher could run the horns while one of your solid state amps could run the woofers.

Using the 555, first remove the metal straps from between the terminals, hook the more powerful amp to the woofers, bottom set of terminals, then the other amp to the top set of terminals to drive the horns. The 555 probably only has one set of preamp outputs so you will have to use a "Y" adaptor with the single end to the preamp, run one leg of the left to bottom amp and the other left to top amp, then do the same with the right. The 545 on woofers and 535 on horns should make a nice combo but as mentioned being able to adjust one amp or the other gain really helps tailor the sound.

If you try it let me know what happens.

Since the Heresy only plays down so far I'd set the main speakers of your HT to "small" and let the sub carry the low end up to about 60Hz or so. This may help there. Out of curiosity what are you using for a center channel speaker? If interested I have an Academy in great condition.