I have an AV receiver (Yamaha 740) which has 6chanel extra input jacks. These jacks can be used for discrete multi-chanel input from a source, for instance DVD/SACD player. When this 6chanel is used, receiver automatically turns off the digital sound field processor. From the musical point of view I haven't understood the superiority of 6chanel comparing with the processor. Any idea or explanation that simply I may understand?