Audio Systems: Aftermarket Subwoofer install for Bose, alpine amplifier, external amplifier

Question
Okay, I'm faced with a tough decision.  I have an 02 infiniti I35 with a bose sub in the rear deck.  My last car had 2 10's and nice tight bass.  I'm trying to grow up but I miss my sub.  I want to add a single 12 but I'm hearing mixed reviews about adding an amp to the exisitng Bose system.  I hear that it will overwork the Bose system and I've also heard that the hi low converters are a short term solution and eventually I'll have to switch the entire system.  I love the factory look in my car.  But am I stuck with the existing sound?  

Answer
you can do that the hi/low interface needs to be made for the bose system  or you can taping to the same lead from the factory woofer and get the external amplifier your the single 12  

i work in that car before i made a ring from the old small woofer and replace it with a 12 freeair kicker and add a 90 watts alpine amplifier the trunk was clean and the bass was 4 times louder  no box to do that you need to find a FREEAIR SPEAKER pioneer,kicker,Kenwood,
good luck