I have two music-boxes 100W/4 ohm.
Could I use these for the pc, have the output connectors of the pc(integrated) enough power or should I find something like an active or passive amplifier(if avaiable) for this ?
The standard output of a 3.5mm audio jack (those typical to PCs) is about 1/3V.
Headphones typical resistance is between 16 and 600Ohms (most common headphones are 16-32Ohms).
Your speakers require MUCH more power than the standard output in order to drive their drivers and will require an amplifier of some sort in order to function.
I have run a similar setup in the past. I used adapters to convert the stereo 3.5mm output from my PC to the RCA input my amplifier needed and it worked just fine and sounded great. You'll want to check with the amplifier you choose to find the inputs it needs, and here will generally be inexpensive adapters to make the connections.
Maybe this works, thanks, if there is no other solution I have find these following link.
It explains to use an Amplifier with enough Watt powered. It can be used with wires or over Blutooth, perhaps also with good softwares to tune the sound.