well, lets see how well I can remember....

the bookshelf speakers were some midrange Boston Acoustics mated with the Aperion S-8 APR subwoofer. The speakers were capable of 80 hz and up, so I set that as the Xover point on the sub along with setting my receiver for small speakers (which means Xover at 80hz). Realistically, this is too high for the subwoofer, but the speakers themselves couldn't do much below that point. The sound was good, but you could definitely tell where the sub was at.

With my towers (B&W CM-6) there is no need for a sub. These towers are designed to run full-range and are very capable of doing so when it comes to music. For movie soundtracks they can lack a bit of low-end extension, but since I live in an apartment (and I don't want to blow out my neighbors) they are fine.

the reason I recommend towers for you is that you should be able to run them below 80 hz, like to around 60, or maybe even 50. This would allow you to set your sub at a lower Xover point which help it to blend in better, soundwise. Also, the towers simply sound better.

I am fortunate enough to live a short distance from Aperion and I have done some comparing (in their showroom) of the different models. The 533-T is my favorite model for music. They have a fuller, more open sound, with better imaging than the bookshelf version. And they're quite nice looking in either of the finishes (though I would love to see a walnut or maple finish added in the future).

Another option to consider, depending on your desire for SQ, would be the powered towers. The nice thing about these is that each tower has a built-in sub with amp (and it has a Xover). The SQ won't be as nice as the 533-T/sub combo, but it will still sound good.