Foster 9, Oh, the value of a re-read of your original post. :-)
To answer your specific question, I would not change the pre-amp gain from 15db unless Joule feels the changes it would make in the optimal position of your volume control (as suggested as possible in my last post) would make it worth while. It seems from your description of your VC's position that you only use it from about 9 to 11 o'clock. If your pre-amps gain as set by Joule were further reduced you would get more use of the VC, presumable a finer gradiation of volume changes and perhaps impedence changes. Al is much smarter than I on these matters, so he can advise or Joule can help.
FWIW. :-)
To answer your specific question, I would not change the pre-amp gain from 15db unless Joule feels the changes it would make in the optimal position of your volume control (as suggested as possible in my last post) would make it worth while. It seems from your description of your VC's position that you only use it from about 9 to 11 o'clock. If your pre-amps gain as set by Joule were further reduced you would get more use of the VC, presumable a finer gradiation of volume changes and perhaps impedence changes. Al is much smarter than I on these matters, so he can advise or Joule can help.
FWIW. :-)