To play only audio from the DisplayPort 6600XT to a monitor, and output video to an amplifier or receiver via DisplayPort, you can follow these steps:
Connect the DisplayPort cable from your graphics card to your monitor, and the second DisplayPort cable from your graphics card to your Yamaha amplifier or receiver.
Go to your Windows Sound settings (right-click on the volume icon in your taskbar and select "Open Sound settings").
Under the "Output" section, select the audio output device that is connected to your amplifier or receiver. It should show up as a separate device from your monitor.
Right-click on your desktop and select "Display settings".
Under the "Multiple displays" section, select "Extend desktop" if it is not already selected. This will allow you to use both your monitor and amplifier as separate displays.
Drag any open windows or applications to the monitor display, leaving the amplifier display blank.
Play any audio or video file and the sound should output through your amplifier or receiver, while the video plays on your monitor.
Note: Depending on your specific graphics card and settings, the steps may vary slightly.
PC Hardware Specialist