Wire An Aftermarket Subwoofer To BOSE Or Stock MS3 Stereo

Originally I used the subwoofer to hook up my loc... It hit harder but sounded horrid had way to much bass it over powered my entire system. Changed it to this method and it is so much cleaner. Might not hit as hard but at least I can hear my mids and highs now! I highly recommend this method over any other!
 
In the pictures listed (d.jpg), is that a quick release/disconnect... thing? In the last picture, there is a black knuckle that your power connects through. Where can I buy that?
 
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