Some audiophiles believe that the more devices you run an audio channel through, each device will degrade the quality of that audio somewhat. I'm not an audiophile by any means and I'm older that my hearing is no longer that well to begin with anyway, but I do run my video such as dvd and bluray through an optical to my receiver, then the tv via RCA and my pc is on a separate amp. I think you can do whatever you like as long as it sounds good to you, and your happy with it.
I tried to use an optical line from the tv to the receiver because they both are designed for optical but I never did get it to work.
My tv and bluray use the built in DAC in my receiver, which is a Harman Kardon AVR 520