There is a slight missunderstanding here. ED didnt say sound engine works on a separeta core but it works on a separate thread. Just reminder most of the processors have more thread than core(Hyper threading). Although there is no linear performance increase(It is around 20 percent) but again most of the CPUs can process more than one thread. For example all the I7 900 processor have 4 cores but they have 8 threads.
However only ED can know real performance implication. If you really would like to see what the people use for gaming please visit the Steam hardware survey. You will see more than 50 percent of the people have dual core processors and the rest divided between quad, hexa and single (8%) cores. I believe this is a good indicator.