Q: still being somewhat mysterious to me in terms of understanding low vs high
I think of Q for a bass driver/cabinet combination as unit-less ratio that describes the slope of a roll-off curve. It is associated with a variation in sound. Qualitatively, I would say a low Q bass (0.7 or lower) sounds "dry or restrained" and a high Q (approaching 1.0 or higher) bass sounds "fat or boomy". It can vary some with the driver and the room.
High Q values do provide greater SPL, but create a muddier sound that masks bass detail. If you have Ray Alden's book, Speaker Building 201, look in the chapter on sealed bass cabinets and look where he discusses how high Q bass alignments allow bass drivers to ring or reverberate, but low Q damps the ringing, at the expense of SPL. There is a good figure that compares the frequency vs. SPL curve to the SPL vs. time curve of different Q values. (If I had my book at my fingertips, I'd tell you the page number.) Basically, low Q = high fidelity, but there seems to be a wide range in individual tastes for this.
In general, the larger the sealed cabinet, the lower the Q. Below is a combined plot of several different sealed cabinet volumes for the same woofer, a JBL 123A. I did this several years ago, but kept the result. You can see volumes ranging from 2.0 to 5.9 ft³, and calculated Q values ranging from 0.7 to 1.0:
Q=0.7, dark blue curve, F3=38.8 Hz
Q=0.8, red curve, F3=44.4
Q=0.9 green curve, F3=50.5
Q=1.0 turquoise curve, F3=56.7
I didn't calculate a cabinet volume for lower than 0.7, such as Q=0.5. This is the so-called critically damped Q value, but for this driver it the cabinet would have been way too large.
