Best Buy did this before I realized how crappy they are. I was just wondering is this bad if later on when I sell my car can I hook up old stocks again? I was also wondering what these active speaker things are?
http://www.cardomain.com/memberpage/617623

 

looks like they bypassed somthing to get a signal. if you ever go to sell your car just re match all the wires backtogether andytou shoudl be ok in our maximas alot of time some modification is required to make aftermarket sound systems work

 

You can hook up old stocks again - although the amp looks like it got bypassed and is no longer used. Best Buys should have unplugged the amp and looped the speaker connections together instead of doing what they did - nissan has a loop connector just for that job.
That way you could have installed the stocks & hooked up the amp again.
The active speaker system used here is different to the Bose unit everyone else has problems with. In this case, both Clarion & Panasonic make this amp for the rear speakers, which gives a total gain of 10-15w max. Of course, the better the rear speakers are, the more noticeable the gain.
I found another amp at a junkyard and wired my fronts the same way to give a better balance. The second amp sits under the stock head unit - pictures to come...