You can do it like Mechans says but he's right in that you may be pushing your Sony harder than it was designed to. If you end up trying it, I would suggest you start with very low volumes at first and if something doesn't sound right, shut it off right away.
Another factor that may be very important is volume. You will have no way of controlling volume independently for each pair of speakers. Assuming the amp can handle both speakers, one speaker may be more efficient than the other. Basically, one pair would play loud and the other would not be. If you keep increasing the volume, you risk damaging the speakers.
Another factor that may be very important is volume. You will have no way of controlling volume independently for each pair of speakers. Assuming the amp can handle both speakers, one speaker may be more efficient than the other. Basically, one pair would play loud and the other would not be. If you keep increasing the volume, you risk damaging the speakers.