Trickyg

Hi, Last week I collected my new Octavia vRS, which is my first Skoda and so far I am loving it. The only issue I have is the speakers in the car. I'm sorry to ask a question that I guess may well of been asked several times before, but has anyone put in an under seat subwoofer? If so any recommendations as to which one, or any other suggestions that you may have to improve the sound. When the volume is up fairly high the speakers don't sound too bad, it's the lower volume that I need more depth of sound. My last few cars have had either a Harman Kardon or B&O system which both have a decent low volume depth of sound. Thanks