How can you evaluate a system with highly processed music?

Each to their own.

But can you really evaluate a system by listening to highly processed, electric/electronic music? How do you know what that sounds like?

I like to listen to voices and acoustic music that is little processed. 

Instruments like piano, violin, etc. 

And the human voice. And the joy of hearing back up singers clearly, etc.

Even if full instrumentation backing a natural sounding voice.

(eg.: singer/songwriters like Lyle Lovett or Leonard Cohen)

There is a standard and a point of reference that can be gauged.