Wasnex, I agree with the rule of just don't argue with the sound crew. You can volunteer gear, but you may find that they don't like to do that because when they did in the past, they found out the gear was faulty during the show. Ultimately it was the tech's fault for substituting unknown gear for known good gear. I would always mention your nice DI at setup, that way they have time to talk to others at the show and maybe they might use it. Usually what DI you use live only really matters when you need a high impedance pickup for say piezos, as not all DIs can handle that, or the signal is really hot so you need a passive DI. They usually just want the Bass DI out to send to the subs. A mic on the cab doesn't sound as good in the subs. The mic on a nice cab does sound best in the mains though. So you want them both at FOH. You will have a hard time telling differences between decent DIs once the signal is band passed at 30hz-80hz at the DSP. It is up to FOH to have enough EQ to make it sound right at the subs at that point.