JBL vs Standard Audio

I've heard the standard audio setup on the Prius, and it wasn't too horrible. Although I'm used to aftermarket audio systems, the factory Prius setup wasn't that bad and definitely do-able for a daily setup.

How much better, or worse is the JBL system? I really want to keep this car stock for the most part, but it needs to have a decent audio system. If I'm okay with the standard system, can I expect nothing but improvement going with the JBL factory setup?

Does the JBL setup have a dedicated subwoofer?