Flx6, Bluetooth speaker and subwoofer

Greetings, I just got my flx6 gt and was wondering about 2 things 1. As controller has soundcard, there is limit on volume, thus the outgoing volume from my wireless speaker is much lower than if I would just play only on speaker. Is red lining allowed If it is not constant? Just sometimes hits red 2. So let's say i still have wireless speaker as a main source of sound. Is it possible to connect subwoofer for extra bass? If yes, how?