You can only change the LFE by +/- 10, and only on DTS, not on DD5.1. There is a reason for that; has to do with the way the track is recorded. Advice I've heard and read is that when you crank the LFE in DTS, you are adding to a level that has already been adjusted.

You can change the sub's gain/volume both at the sub and with the receiver... The sub is always getting both bass and LFE (unless, of course, there isn't any present). I always leave the LFE where it is. ... Mike