I was wondering if its possible to add a sub to a stock stereo system on my 2000 bonneville. I really want to keep the stock stereo in the car if possible.

You need to get a line out converter, it splices into the rear speaker wiring. Then you would have to find a switched power source to power up the amp.

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-Ryan
2004 GTO....LS1, LSA supercharged 525whp, 6MT
96 SSEi...September 2010 COTM........GONE
04 GTP comp G.... December 2015 COTM........GONE
2013 Audi Allroad Quattro

Get a line out converter and tap into one of the rear 6X9's for the sound signal. Get an amp of your choice and hook up the RCA inputs to the amp from the LOC, and then hook up the sub to the amp. Run the turn on lead from the amp to the fuse box under the back seat to the IGN 3 fuse. Your amp will turn on when the key is on the ON position but won't work on ACC. However, if you put the key right in between the ACC and ON positions, the car will be in ACC mode but the amp will run. That is how mine is set up and I have no issues.

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-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles

If you are still going to use the Bose amp for the other speakers, then you also tap into the 12v amp turn on wire coming from the radio to the amp to turn on the sub. Just unplug the connector to the Bose amp and use a DMM to test the wires going into the sub until you find the one that is 12V when the radio is turned on and is zero volts when the radio is turned off.

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bobgto65

2004 Bonneville GXP 62,000 miles purchased 04/13
2009 G8 GXP PBM, M6 9580 miles, no mods, sold 08/15
2009 G8 GT SBM 36,000 miles, modded 430 whp
2002 Bonneville SSEi 203,200 miles (sold 3/2014)

Ah yes, you could totally do that instead and save yourself trouble. My car didn't have an amp in the stock system.

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-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles