Hi, Swampwalker: I went through the same debate about 2 months ago when I bought a pair of 2Wq's ($800 each for subs that are both less than 2 years old). Before buying, I listened to both the 2W and 2Wq, and while the 2Wq sounded somewhat better to my ear, it wasn't a huge difference since I set the "Q" very low anyway for tight bass response.
To get a more informed opinion about the relative merits of each model of sub, I called Vandersteen Audio and talked directly with Richard Vandersteen. Richard said there are two primary differences between the two models, and a third difference which is less apparent. (It might be advisable for you call Vandersteen and ask him if there are any considerations pertinent to the 2Ci -- my experience has been with a pair of 3A Signatures.)
1. The 2Wq, as you note, has an adjustable "Q" control, which allows you to adjust the "tautness" of the bass response. In addition, however, this control changes the contour of the bass response. Set at the "0" level, the frequency response is flattest from 20-60 Hz. As you increase the "Q" setting, the frequency response becomes more and more peaked, so at its maximum point ("10" on the scale), there is an 8 db rise above 0-db. At the "10" setting, the bass quality is also much looser, which emphasizes the bass response for reproducing LFE from DVD soundtracks. This feature can be useful if you intend to use the sub(s) about equally for music and HT.
2. According to Vandersteen, the 2Wq also has a better amplifier than the 2W (his words, not mine). Richard told me that the 2Wq required a better amp to be able to handle the frequency contouring provided by the adjustable "Q" control.
3. Finally, the 2Wq has a somewhat better cabinet than the 2W. I think Richard said it has more internal bracing, so is stiffer and less resonant.
As an aside, you might like to know that the first 2W sub was produced in 1984, so Vandersteen has a LOT of experience building these subs. I was told by my local Vandersteen dealer that Richard virtually sells the subs virtually at cost to encourage their sale. If they sold at the regular retail markup, they'd sell for more than $2000 apiece.
After talking with Vandersteen, I opted to find a used pair of 2Wq's, since the price differential between the 2W and 2Wq is nominal. I advertised in the "Want to buy" section here on Audiogon, and got responses within two weeks.
To close, let me tell you that the 2Wq's add an improved dimension to my Vandy 3A Signatures I never expected. Oh, I expected much more extended, clean bass, but I did not anticipate the increase I got in mid-range clarity and openness. I am genuinely hearing details in recordings (ones I know very well) that I have never heard before.
Last thing to consider: the 2Wq's require a crossover that goes between the preamp and power amp. The stock crossover costs $125 -- it should be included if you buy a used sub, but it may not work with the amp you have -- each crossover must be tailored to the input impedance of your main power amp. You might want to consider buying the much higher quality crossover made for the subwoofer in the Vandersteen Model 5. This upgraded crossover (actually, 2 separate crossover units -- 1 for each channel) uses very high quality parts, such as Wima caps and Vishay resistors, but costs $600 if you buy it direct from Vandersteen. I got a used Model 5 crossover from my local Vandy dealer, and I highly recommend it. I simply cannot tell there is a crossover in the signal path!
In short, I suggest you get a pair of 2Wq's -- you won't be disappointed. These subs integrate so well that they totally disappear. If you get the 2Wq's, I'll be glad to share my setup experiences with you, which should save you some time.