You can buy any sub irrespective of what satellite speakers you have. There is no criteria of matching Sub with speakers.
The typical frequency range of human hearing is between 20-20,000Hz. A good sub should be able to reproduce most of the frequencies within this range. For 100% music floorstanding speakers can deliver good bass response and adding a Sub will give u a deep bass.
Velodyne Impact
Velodyne CHT series
If you want a cheaper option then Boston Acoustics CS 10.