Sorry, one more stereo question

[ANDREW_ATWELL@HP-PaloAlto-om20.om.hp.com]

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     Sorry to beat a dead horse..
     I did what I was supposed to first, I looked in the archives to see if 
     I could answer my own question, but could not find the definitve 
     answer.  Please respond to me personally as not to use up bandwith.
     
     I want to add a powered subwoofer to my Jetta (one 8"or 10"bazooka, 
     Kenwood etc.).
     For the wiring, I will use scotchlok taps to splice into the speaker 
     wires for the rear at the head unit.
     
     My questions are: Where is it safe to draw power from? (these tubes 
     are only a max 80watts mono RMS).  Can I safely tap into the power for 
     the deck?  Where can I tap into for the ignition (amp turn on) wire?  
     Can I tap into one at the deck?  
     
     As I remember, some have said that one of these circuits was weak and 
     would blow my ingnition if I tap into it.  Which one was it, and where 
     would an alternative place to tap into be?
     
     Thanks.
     andy