if the amp supports bridged mode, you should have directions for how to wire the subs in the amp's manual. what make/model is the amplifier, and what is the impedance and number of coils for each sub?
you don't hook them together. RTFM and see if they even support bridged mode first. which RF subs are these? HE2? HX2? you'd be best off just using the USAcoustics amp and trashing the sony.