Unless you have a very good reason* to do it any other way the left and right channels should always be in phase.
*There is a technique of wiring single ended amps and speakers with one channel "double out of phase" as an effort to improve the performance of the amp. The end result is that the sound is in phase, but the electronics are out of phase. Nobody does it because they can sell monoblocks for what a stereo amp costs and its tricky to explain. This technique has basically no effect on amplifiers with balanced power stages, so dont worry about the Bijou, just posting because maybe someone will use it to their advantage someday.