JL has some really nice quality subwoofers, and you don't need to run them at their RMS, you can run it quite a bit under that. You can also tune your amp to not amplify the bass as much. whatever you do pick don't cheap out and use a cheaper company since in my experience the cheaper companies tend to go for loudness rather than sound quality and boast stupidly unrealistic stats. Some companies i like and have heard personally are JL, Rockford Fosgate, Kicker, Polk Audio, and MOMO (which is a polk audio brand).Well the default speakers have no bass. it is the base gt without the special sound system so it doesn't have a stock subwoofer. A 10 with a small amp will not produce great amounts of bass to where it can be heard out of the car.