well, the best idea seems to be to set up with the empeg at 0db (or lower if there is clipping) to give a decent signal to the amp.
Then just change the amp gain to suit.
Slight adjustments are likely to involve reducing the empeg gain a bit, bringing the amp up a bit, so that when you are on the motorway you can increase the volume.
I tend to have mine at -18db for city and -6db for motorway. I take it up to 0 on some noisy roads. I also have voladj set to medium. This means my amp sits at about 3.
_________________________
Rory
MkIIa, blue lit buttons, memory upgrade, 1Tb in Subaru Forester STi
MkII, 240Gb in Mark Lord dock
MkII, 80Gb SSD in dock