I know we've been down this road before and most probably will do this dance many more times.
Although many of the posts have great info, It strikes me that no one is commenting on the elephant in the room;
I'm talking about the sound characteristics of the room your playing in, the proximity of the other instruments and all the other sound variables that we, as bassists, have to contend with in a live situation.
All of the other variables are typically what can be most vexing (vexing is my new word for the day!)
My particular setup: Full Circle, Fishman Platinum Pro, Phil Jones FlightCase 300 and often an AMT mic into the house can sound amazingly good and close to how my bass sounds unamped but..and this is a big BUTT...all of the other variables can negate pr seriously alter what I'm hearing onn stage.
I would be very interested in hearing how otheres deal with or counter many of these obstacles in a live playing situation!
Ball's in your court!