unless its a stereo amp,effects i find it useless.....a double performance would be better......
now mic'ing with 2 mics (not necessarily for stereo reasons) can be useful......
a dynamic up close and a room mic......a dynamic up close off axis and another on......a dynamic on your 2 best sounding speakers(if you have multiples)......
many ways to do it, but this wouldnt be considered "stereo".....