Crossing Left and Right Speakers

There sound should be no different other than reversing the channels of the recorded output left to right and vice versa. 

Unless-

1) Something was inadvertently wired out of phase. 

2) The room acoustics affect the sound of the left and right speakers differently- e.g. reflections, absorbtions, reinforcement of different frequencies, back of room differences- e.g. one side open, one side closed off etc. 

Test this by reversing the output interconnects of the source channels.  If the sound is the same as reversing preamp outputs then it is because of room acoustics. 

does the reversed image sound the same if the amps are non-reversed and you turn your head away from the speakers?