Dumb Question:

What is Stereo?

I know what stereo is its a 2 channel format which is used to create a realistic image of the sound.
Making it sound like it is coming from different directions in front of you.

Assuming that is correct why do we need Rear right and left channels?

All the High end Car Recievers have Front Left, Front Right, Rear left Rear Right and Sub do they actually compute
and create rear sound from a 2 channle source or do they just split the front sound and pipe it to the rear.

Sub I understand, to me it would make more since if high end recievers had High, Med, Low and Sub outputs but that is not the case on most units.
So riddle me this

I am listening to CD#007 or Mp3 Track #54112 what is being played out the rear channels ?

I think the Empeg unit just splits the front channles to the rear?

The reason I am asking it I am re-building my stereo and I was considering using the diamond s600s Speakers they have
A cross-over with a rear fill output for imaging this would allow me to use a two channle amp and relax the load on my
poor little 170Amp alt.