I have the Creative Inspire P380 which includes a subwoofer. Think these may now be superseded but they are very effective for playing music, films etc. on my little laptop. I would think that a subwoofer would be a great asset to the two satellite speakers, on their own they wouldn't be much better than your present ones.
Best Android apps 2015/2016: Best apps for your new phone or tablet - what apps should I download?