Just posting this just for general purposes, because i sure most of us know this already.
Well, i run 7.1 multichannel from my Pio 51fd to my Pio 49txi. I had been putting off buying some good (rca) cables until today. The ones i were previously using were the cheap, flimsy red and white ones. I had also been running a long rca cable as a subwoofer cable
I finally got around to getting a subwoofer cable and some really thick gold plated audio cables from radio shack...all i can say is wow, what a difference.
If you are a 7.1 multichannel user(like me), get good cables, not necessarily expensive ones, but good ones that are made for audio.
on side note, if anyone has experienced popping with their 51fd while using multichannel, switch the 51fd to "large" speakers and that will solve your problems