IMO I think that applies more to a competition SQ car or the "true audiophiles" that you mentioned who judge their system by those standards and will go to great lengths/spend countless hours and $$$ trying to achieve that level of perfection.SQ is more than tonal accuracy.
Sound stage and good transients are also very important to true audiophiles.
Subs are very important as are the mid and high drivers. However Transients, EQing, and aiming and time aligning are MORE important Transients are largely affected by install and system design, EQing improves transients, and aimingand time aligning have everything to do with time put into the install.
I'm not an SQ expert, but I can tell you that.
I side more with the OP and think that DD SQ is more about tonal accuracy and an over all pleasing sound that makes the listening experience enjoyable. I consider it an apples to oranges comparison, but both can make the listener happy.
My only "suggestion" would be to try and demo some of the subs you're interested in, obviously using your choice of music.
I have what "I" consider to be a very good DD SQL set up and enjoy it every time I listen, whether it's some mellow 70's rock, cranking some 80's metal, or old school hip hop. It does all that "I" ask of it and more. Many on here would laugh at my set up, but I built if for me by relying upon the opinions of others at times, but the final decisions were based upon my ears.
It sounds like you know what you want, now you just need to find the subs/equipment that provides that sound. Plenty of good choices out there //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
I also believe that a lot of the "install dependant" factor has to do with NOT making install mistakes: box wrong for sub, too much/not enough output to match rest of sytem, SPL sub for a SQ set up, poorly built box that leaks, etc...
EDIT: fixed typo
