I agree, the amp sims are very usable.
In theory, you should be able to use the DI Out straight to the desk (without the need for the PA DI box), and get a usable sound. Though I would spend some time in rehearsal plugged into the PA, tweaking your sound so it works. That's the whole reason I bought a B3, but I admit that I'm GAS-ing for an amp as well now!
You could also plug it into your computer & install a recording package to see how it sounds "on record" so to speak.