I am using Audio systems from a long time as I am learning music. The main things you should keep in mind while buying audio system is that buy which that suits you that means buy according to that how much you want to amplify when you are listening music and which category you are listening, whats your room size where you will keep your system, with what you will attach it.
first of all select the the category of audio system like 2.0, 2.1, 5.1, 7.2 etc. as it depends upon your power and room size or the base you want. Now if you want your audio system to run its maximum range then but a good brand as because if you opt for cheap one then you will find the audio distorted at max volume. If you buy large speakers like 5.1 or 7.1 then you will not get soul out of them if your room is small, its good for halls. @.0 is best for laptops use, they are portable and good at moderate sound. While buying bluetooth portable speaker check whether the sound is not distorting at full volume.