Dynavoice speakers question

They are very small and have very little bass, if you're budget constrained you should check for second hand speakers on Blocket, Tradera or Hifitorget. It will, with a little effort, reward you with much better sound quality.

I haven't listened to the S-3s but have an earlier version of the S-4s and they are good speakers for the money, IMO. Even though the specs say they both go down to 50Hz I would guess that the S-4s will do so with less distortion, due to the bigger cone area.

As mentioned above both of these speakers might lack some bass, depending on how you will use them. If you want to play loud and/or if you have a large room they will sound a bit thin. If you will use them for near field listening sitting in front of your computer, for example, or have a smaller room and listen at somewhat lower volumes they will probably be fine.