Rel vs. Vandersteen vs Audio Physic subwoofers

I like all three constructors (not helpful, I know). For MUSIC alone, I have a slight preference for the Luna, ONLY in stereo (i.e., two Lunas). This MAY be due to the fact that the Luna was allegedly voiced using jazz & classical -- i.e. reproducing mostly acoustic & electrical instruments.

As to the 10Hz... I would expect any of the other two to be more authoritative in reproducing sub-bass (i.e. the SF channel in HT). BTW, loud 10Hz is not very good for the structural integrity of the house you know:)

Because they produce spls with more ease. It's not only the extension that counts, but also the (dba) level where the device maxes out (& distorts or, worse, develops a problem).
Cheers