In my earlier post, I forgot to mention one other factor: placement of the Vandy subs in your listening room. I have talked directly with Richard Vandersteen on this subject, and his guidance (repeated in the user's manual) is to place the 2Wq's in the room corners if possible, but within a few feet of the main speakers. Corner placement substantially improves the bass loading into the room, and having the subs fairly close to the main speakers yields better integration of the frequencies.
If you have your main speakers on a long wall, it may not be practical to place the subs in the corners of the room. If so, you should still have the subs fairly close to the back wall. In short, the closer you can place the subs to room boundaries (back wall OK, corner best), the better the Vandy subs will perform.
The other point I did not specifically address is having one Vandy 2Wq versus two. The 2Wq was ideally designed to be used in pairs, and if you are using only one, you WILL have less output. More than that, if you have only one 2Wq for music applications, you will be losing phase-related information form the music signal, since it is necessary to sum the L+R signals at the sub's inputs.
Vandersteen produces the V2W subwoofer for HT use, and it has a 12" passive radiator on the front panel which increases output about 6 db. The V2W also is driven directly from the LFE output on the pre/pro, unlike the 2Wq which gets its signal from the power amp outputs. If high volume levels are a primary desire, then you may want to think about selling your 2Wq and buy two V2W's instead. This would provide the phase-related information inherent in the music, plus very high volume output.
When I originally bought my Vandy 2Wq, I had only one sub in the system -- it was decent, but not what I had hoped for. When I added a second 2Wq, it was whole different matter -- the bass is tight, full, extremely musical, and fully adequate for HT. If you do not have a pair of 2Wq's in your system, you are NOT hearing the performance that the 2Wq's can provide. In short, I suggest you get a second 2Wq -- I think you will be very pleased with the result.
Last point: using the crossover, as I said in my initial post, isn't optional. Not only does it directly impact the performance of the sub, it also impacts the performance of your main speakers. One of the less-discussed benefits of using a subwoofer in a full-range system is the reduction of IM distortion in the mid-range and woofer drivers in the main speakers. This yields a significant improvement in both apparent speed and clarity in the critical upper bass and mid-range frequencies.
Hope this helps. I -- and some other posters on this forum -- have spent a lot of time tweaking our Vandy subwoofers (2Wq, V2W, and the sub in the Model 5). I can't speak for others, but if you'd like to talk with me by phone about optimizing your 2Wq setup, please send me a private E-mail containing your home phone number, and I'll be glad to call you.