Bass Guitar Amps are created for lower wavelenghts, as the bass guitars demand more power to move the airwaves throughout the sound system. It is very important that you purchase the correct amp for your bass guitar so that you are getting the sounds that you are wanting to achieve.
Using a bass amplifier with your bass guitar will provide you with the electrical power to make sure you are loud enough to be heard by your audience. The bass guitar iself doesn't make enough sound, the amp is what fills the room with vibrations, the higher the wattage of your amp then the higher the sound will be. If you are practising and playing at home then you will not need the highest wattage, as only you need to hear the sounds produced - this will also ensure that you don't annoy your neighbours! However, if you are performing then you should consider a higher wattage, something that has over 200 Watts as this ensures you have a powerful sound produced.