That's awesome JT! I have never seen that soundbar until now. Gotta be the best one out there by the specs and Bazooka is an established name in car stereo. Looks like it might be too big for a P5 though?
As for hooking up a subwoofer to that soundbar, you would need a separate amplifier or a powered sub. It has audio outputs but they are low level RCA's and not powered. That's why roc said that his kicker sub just hummed, he was sending a low volt signal to the sub, just frequency and no power. The shallow mount that he has now, has an onboard amp.
In regards to matching wattage of sub to the stereo output, sub amps are usually much higher powered than for full range speakers. The only time matching wattage comes into play is between an amp and a speaker. If a speaker can handle 75 RMS, ( rms meaning continuous power) then you try to match that with an amp that puts out close to the same.
Hope I'm not coming across as a know it all, I hate those guys. Just been playing with stereos as long as I can remember and try to help guys out with what I've learned along the way.