I've lost count of how many gigs I've done using just my bass, MXR M80 and the PA. Even if I take an amp, we take a feed from my pedalboard into the PA. There are problems in the system (broken equipment, user error, mismatched levels) somewhere if you can't get a great sound from just the sansamp into the desk. The same goes for you spinynorman, the DI on your portaflex is specifically made to do just what you asked it to, it should work and if it doesn't it's broken.