Okay guys, I have a 2009 S with the HiFi system. It is decent but lacks some sub power. I wanted to get a powered sub to fix them problem. Can I add a sub on the stock system? And if I can, what would you recomend as an option that doesn't take too much room up, like a hidden under the seat sub? Thanks NAM!

 

This is one of the smallest "all in ones that I have seen. http://www.crutchfield.com/p_777B8PT...PT.html?tp=114

Not sure if it will fit under the seat. It has high level inputs so you can tap into the front speaker leads for the feed.

 

The frequency response on that thing sucks (40-200hz) ... i would look into a custom solution something that can be hidden away like the Intergral audio sub or something cheaper if you don't want to spend that kind of coin...
Tc sounds Epic 8 can be had for less than $200 kicker zx 300.1 can be had for @ $130 and a custom box design can be had from My buddy Peter W. Kulicki (pwkdesigns.com)for $50 that should yield some great bass...