I use the same two basses for all my gigs. One is active with rounds, one is passive with flats. I sound check them and choose the one I prefer on the night.
All my basses sound great with the controls on the amp set to 12 o'clock. Buy the right amp and you probably won't need the EQ. Very bad sounding rooms can throw a spanner in the works, but usually the master volume is usually the only control I use.
IMO if you regularly have to take big swings at the EQ to get a sound you like, you bought the wrong amp.