KJ, if you use HDMI direct to Yamaha 2600, you will only get pass thru (untouched) signal to the TV.
Your HD content will be better with HDMI. Whether your SD content is better will depend on whether or not the scaler in the Yamaha is better than the scaler in the TV. My older Panny sucks but the Sony is supposed to have a decent scaler. So, trial & error for you. Try it both ways and then decide. Also, when using the component input to the Yamaha, try setting it up for 1080i output and then try 720p output and see which looks better on your TV. You have to tell the Yamaha what you want it to do. It will only upscale if you set it up that way (see manual)
So it really depends on which upscaler is better for SD content (TV or Yamaha). (Sorry - I know that my signature showed Sony KDS-R60XBR1 but at last minute I found used Panny that was OK and decided to wait for full 1080p and LED/Laser instead of HID Lamp)
If the TV is better, go HDMI all the way and you have one easy connection and no input switching to worry about. If the Yamaha scaler is better, hook up both component and HDMI from Sat Box to receiver and switch from one to the other depending on what you are watching or just accept whatever the upscaled input looks like if it's good enough.
Also, your TV has two HDMI inputs. Use one for a direct HDMI connection from the Sat Box and then compare. This is nice if the TV scaler is OK and you don't want to turn everything on all the time.
Good Luck.