Rogers 3/5 A speaker + AB subwoofer ??

The Biamp guy is nuts. If you have the 15 ohm version,(much better), crossing them over to a good sub increases thier appearent size and transparency, but a good sub x-over is hard to find and you can mess up the purity of the amp/preamp direct connection.Overall, I'd say dont do it unless you really have proven combos that don't detract from these important parameters.

biamp the things 100 watts on midrange, 60 on tweeter, audio research, direct output mark levinson 39, amazing but still need to experiment

AS you might suspect, there is a trade-off. With the subwoofer you will pick up another octave of bass, but you will give up some of that marvelous transparency. I sold my subs and bought a better (tube) amp, and have never regretted it. DO place them on solid stands of at least 32".