Dawg,
For $600 you can understand the bass shortcomings of your current speakers with a Velodyne SMS-1 sub controller (X-over, room analyzer, PEq). First, just use the analyzer portion of the SMS (no sub) to analyze your speakers in your room below 200hz. This will conclusively demonstrate that you want a subwoofer - just predicting here, but confident from my own experience.
As to Stanwal's philosophy vs. Bob Reynold's philosophy, home theater experience is not Bob's reference point here. His position is based on data from performance tests, Stanwal's on his listening experience and that of some reviewers. My own experience is too limited for me to dismiss either opinion, but I am personally more comfortable with Bob's approach. I have researched the numbers that Bob linked to and intend to audition those models that perform well. Unfortunately, i am just starting this effort...so no conclusions, yet.
Thus far, I can only ofer a few observations followed by one bit of speculation:
1) "Tight" bass seems to be a function of a spec called "Group Delay" (this is not gospel and is subject to some debate). Sealed boxes tend to minize this spec.
2) Loudspeaker distortion in the deep bass is orders of magnitude higher than elsewhere in your system. In subwoofers, a large driver in a large, vented cabinet tends to minimize distortion.
3) JL subs (very expensive) and SVS subs (less expensive to much less expensive, depending on model) both perform very well on both tests, the JL's show higher distortion but lower group delay, the SVS vice versa (per the link Bob has provided).
My observation:
The Velodyne SMS-1 will (with some work) allow smooth low frequency response below 30hz in a decent room as well as seamless integration with a variety (probably not all) of main speakers. The X-over and PEq in combination with the visual aid of room analysis are very effective tools for dialing in a seamles match.
Marty
PS - FWIW, the SVS Ultra 13 (app $2500 per pair) offer a combo of Group Delay and distortion specs that are hard to beat at any price. The less expensive SVS ($1100/pair) aren't far behind, particularly if you believe that extremely controlled Group Delay performance is not important.