3800 has 4 in/1 out HDMI slots.
Traditional/Ideal connection would be connect a HDMI cable from the "Out" of the 3800 to your TV, then you connect another HDMI cable from one of the "In" (I believe it's labeled DTV/CBL) to your cable/satellite box. If that works, you don't need to connect another optical cable from your SAT box to your 3800.
In my case, I have to do it differently because I got a 1-2 second black out delays every time I switch from a SD channel to HD channel. To resolve my problem, I connect one HDMI from my SAT box to TV and one optical cable from my SAT box to my 3800.
Does your Onkyo DVD/CD player has optical out as well? If it does, use it instead of the red/white RCA cable. It will sound a lot better. You should also connect the SVideo cable from your Onkyo to the Yammy 3800 so you can switch between cable and dvd viewing with the receiver.