I have two sets of speakers: one is set of stereo loudspeakers with a subwoofer (not 2.1, just a sub with a low-pass filter) and the other is a set of stereo speakers with a headphone jack, used solely as an inline amplifier and volume control for my headphones. Currently I have my PulseAudio output set to "Analog Surround 4.0 Output." My motherboard has output jacks for front, side, rear, and "Ctr Bass" which I assume is meant to be a subwoofer channel, for 6.1 surround capability. I have one set of speakers plugged into "front" and one set plugged into "rear". This gives me approximately what I want: I can listen to the headphones or the loudspeakers just by turning on the appropriate amplifier.
However, I'm not sure that this is quite what I want. I'm assuming that the output of front left and right channels is the same as the rear channels, but I don't know that for sure and I'm seeking reassurance. Just in case I play a game or use some other surround-sound source, I'd like to ensure that these outputs act as two stereo outputs rather than one surround output.
Also, I'd like to be able to send audio from a particular client to an output of my choosing. paprefs does not seem to offer this level of fine-grained control. Does anyone know how I can achieve these things?