Over time I have accrued two pairs of older speakers by various yard sales or gifts from friends. One is a pair of Sony bookshelf speakers rated at 60w max power and 8 ohms impedance, and the other is a pair of Pioneer towers rated at 160w max power and the same impedance. I would like to drive all four at once using my PC as the audio source, if possible- what sort of amplifier should I get for this task, and how should I wire my speakers up (in case I get a 2-channel and need to connect all four at once, for instance?)
The green "line out" is for the main L and R channels, connect the 3.5mm to that and the input on the amp, then connect the tower speakers to the amp. Since this does not come with the audio connection cable use the 3.5mm to RCA adapter that came with the other amp to connect it to your PC.
The blue "rear out" is for the L and R surround speakers, connect the 3.5mm M/M to that and the AUX input on the amp, then connect the small surround speakers to the amp.
Set your PC to "quadraphonic" in your sound settings (example here and also in the previous link), do the sound test and adjust the volume settings to your liking.