If your nVidia card has a dvi and hdmi connection, connect the dvi output directly to your tv, connect the hdmi to your avr. Set the tv as display 1 and extend the desktop to display 2 which is you avr. When you turn off the tv, the sound will stop for a few seconds but then come back on. This works perfectly for me.
Alternatively, you could get a Gefen HDMI detective. It's a pricey solution but it works for me.