woofer option that wont take space in trunk
 

One thing I am not too crazy about my car is (like most of you) the sound system.

While I don't mind the awkward control and some what laggy interface, I just cannot enjoy the sound coming out of the speakers.

My old car (2000 Corolla) had better 'punch' than these.

Here's the question,
is there something I can get that are

1. not that big, something that will fit under a seat or something
2. plug and play, easy enough for me to wire and install myself
3. give nice bass, while avoiding shaking my car

Take a look at OEM Audio. http://www.oemaudioplus.com/mobile/systems/frs.html

You're unlikely to fit anything under the seats, unless you raise your driver's seat all the way up.

You can put a sub in the spare wheel space in the boot, or go for a discrete side-mounted box like the JL one.

My amp is installed under the drivers seat, and the sub is (going to be) in an integerity concepts box that mounts in the passenger corner of the trunk. I know there are some people who just replace the spare tire well with a sub/false floor, and that turns out pretty sweet.

The issue the guys who installed it had was that the stock head unit doesnt have RCA outs, meaning that you HAVE to tap the wires from the HU to get audio for the amp.

No such thing as plug n play for the factory HU. (except canada? I heard?)

They ended up using some kind of in-line converter to get from the factory harness to some RCA outs. Still not exactly plug and play.

If the bespoke unit in the US is the same as the pioneer upgrade in Canada there are 6 channel rca pre-outs on the HU.

I got my amp on the passenger seat and a "flat" sub on the back, Link to the model

The best way I can explain it is, it's not seated flush on the ground it's slightly tipped over at an angle and the top of it is bolted to the roof of the trunk with a metal L.

My car is at home but when I get home I'll take a pic of it.