I presently own Logitech's Z-640 5.1 PC speaker system. Now from what I can tell it uses the same serial port style connector as the Z-5500's control module/decoder. So here's my question; if I called up Logitech and ordered a replacement Z-5500 decoder module, would it work with my Z-640 satellites and woofer? I really don't want to buy a new ~$400 5.1 speaker system when I already possess everything but the optical input and decoding device. I'm attempting to get optical from a PS3 to my 5.1