Howiecreate is right on this, you should listen carefully the live mix getting out the ls9 and maybe try to be there for the soundcheck.
has a retire live soundman, depending on a loud instrument are on stage, what you will listen out of a LS9 will not be as what you hear live.
Sometime when the bass player came whit is 8x10 inch cab, you don't need bass in you're mix, cause is all ready too much in the room,I seen that before So pulling a mic, taking signal of the Ls9 and making you're own mix on the 664, can be a good choice .