I would tend to agree here. One thing I appreciate about Hsu is that even their budget line of subwoofers offers competent engineering and good performance. Obviously the larger and more expensive VTF-2 is going to open up the possibilities of deeper bass and more clean output; however, I'd daresay that even the STF-2 won't have a big problem cleanly getting you to lease breaking levels.
Just to toss in my 2 cents, as I stated in my first post on this thread, if I were building an ideal system for this case, I'd probably not bother with towers at all, but instead aim for a higher quality bookshelf speaker.
Big tower speakers have obvious advantages, but the realities of apartment living and the utilization of a respectable powered subwoofer reduces them considerably. On the other hand, bookshelf speakers have their advantages as well: a smaller cabinet and fewer drivers equates directly to reduced cost and occasionally reduced cabinet vibration as well at the same level of refinement. At the same level of cost, I don't think it to be unreasonable to expect higher quality drivers, crossovers, etc from a bookshelf than a tower.