You Do need a DI to run the bass direct through the snake. You'll also need a DI for an acoustic UNLESS it goes into some other preamp or amplification device first.
If you just get a good DI all your problems will be solved. Plug whatever you want into it and then it into the snake or console and you are ready to roll. Don't make it any more complex than it has to be. DIs are cheap and worth the investment.