Richie, what Peter was referring to isn't something which is necessarily done by the user intentionally. Two different amplifier channels, even in the same receiver, may not be perfectly matched as to output. This can result in one section of the speaker having a slightly higher or lower sound level at the same setting than the other section, as compared to the situation when both were driven by the same amp channel. So, this could result in a slight audible difference, but wouldn't be an improvement as such, but simply an imbalance from what was intended by the speaker designer. Subjective impressions can be, and often are, misimpressions, but that isn't necessarily the case here, although that type of biamping has no factual basis for actually making an improvement. The same power available from the power supply section of the receiver is simply routed through the output transistors in two channels instead of one; no increase occurs.
Enjoy the music, not the equipment.