i agree with everyone in the sense that it takes some time (sometimes a long time) to integrate a sub in with your speakers (towers or bookshelves). i can't tell you how many weeks i adjusted back and forth, and fooled with the crossovers until i found the right setting for music, and the right settings for movies. i have some very simple Infinity Entra 1's paired with a Klipsch RSW-12 reference sub all run by an Arcam A-75 integrated amp. i thought i would have needed to upgrade my Infinity bookshelves once i bought the very pricey Klipsch and the Arcam, but i was wrong. they just brought out so much more of the Infinities than i ever imagined possible. the point there is that your system components and or amplification of course play a major role in how well everything meshes together. also, one of the main reasons as to why my setup worked so well together was because of the Klipsch sub. it is a sealed deisgn with one active driver and one passive one. compared to all the other ported designs i auditioned (Velodyne included), the sealed Klipsch throws out an incredible amount of clean accurate bass, which works very well with both movies and music. it is funny how you observed the Velodyne as i also made the exact same obervations; and they were being run from some very high end Krell equipment. the Velodyne HGS 18 i think(?) just sounded to uncontrolled and too floppy. i've also heard it on many other systems and have come up with the same results. but a lot of people like them for movies and their huge amounts of bloated bass apparently sounds good for explosions. but that's about it, imo. based on what i know about speakers and room interactions, i think that if your room is relatively small, bookshelves are the way to go. when i first bought my Kllipsch, i though it would benefit more by pairing it with my Kef Q5 towers...but my room is simply too small for that combo...that combo will be used for another day when i can move my system into a bigger room. but for now, my bookshelves certainly integrate very well with the Klipsch RSW-12. i think if you can find a very accurate sub (a sealed enclosure, imo), you will be ok with trying to integrate whatever speakers you buy. i also think that if a challenge is presented to you in trying to integrate a combo, that that challenge not only helps you learn a great deal about your particular system (the strengths and weaknesses), but it is also a fun process...at least i think it is
good luck and let us know what you end up getting; even if it is months from now.