I have a new Onkyo HT-R510 receiver (came with the Onkyo HTIB system) and a new Mitsubishi DD-8040 DVD player. I've got optical audio connected from the DVD player to the receiver. At the store where I purchased it, the salesman told me that despite using the optical audio connection, I should also hook up the 5.1 CH Audio out jacks to the receiver. But, when the delivery people came, they said that I should only hook up the optical audio, as the 5.1 CH Audio connections would be superfluous or maybe even override the optical connection. Can someone help with this? Is there some reason to hook up both connections? What is the purpose of the 5.1 CH output if I've got the digital optical connection? Thanks in advance for your help.