also, forgot to add, i always cross over all my speaker at 80hz, even if they are bass capable because of the benefits this has, first off, with bookshelf speakers, even though they can extend down to 55hz, let's face it, 5.25 inch woofers are nothing more then good mid-range and mid-bass drivers, they are not able to cleanly reproduce bass frequencies let alone sub-bass frequencies (below 40hz). they just sound much more open and clear with that high x-over point rather then forced with a lower one, and, your saving amp power and giving yourself more headroom. secondly, with larger three-way speakers, you are in essence creating a four way system loosely following the 3 octave rule with the woofers covering only the mid-bass sections and the sub handling the lower bass section. it just sounds better to me.