You can't connect the speakers directly to SCART or phono outputs. SCART connectors have audio output on some of the pins, but like RCA phono outputs they are "line level", which is a very low power signal designed to be passed on to an amplifier which then provides enough power to drive speakers.
So what you need is an amplifier. If you just want stereo then any hifi seperates or all in one system will do it. If you want full 5.1 surround then you need an amplifier which is made for the purpose. I suggest you start by visiting your local electrical shops and see what they have, or try a home cinema magazine - they are always full of adverts and advice.