In many cases the result is not the same when you bridge a stereo amp compared to a true mono block amplifier. When you bridge an amp, you are summing the output stages of the two channels which has the same effect as wiring a load in parallel to the amp. So if your speaker load is 8 Ohms, the amp really sees 4 Ohms when configured in parallel. When the amp is bridged, it produces the more power by increasing the output voltage but the current capacity stays the same. I'd be very careful about using a stereo amp in a bridged mono configuration if the speaker in question is a difficult load to drive for a regular configuration amp.