Then ,if I got it, the S4 isnt your choice since u cant connect CDJs or TTs to it.
What is your old setup anyways? If you have a “traditional” setup(Mixer 2x some sort of CD-Player) and if you dont have a programm for DJing yet and only want to get your mp3s running, why not take a look at some CDJs ,either Pio or Denon I would recomend (every1 I know who owns CDJs says Denon and Pio are the best out there), that can take in a USB Flash drive. Then you can put your Mp3s on the flash and your good to go.