ATC Audio in Headphones Only

I recently bought a Plantronics USB headset and tried with FSX for the first time last night. I discovered that I now have two audio devices present in Windows-XP and within FSX. In Windows and FSX (sound settings), I set sounds(.wav) to my PCI Sounblaster card and voice to my Plantronics USB device. With this setup, the default FSX ATC audio voices now only comes through my headset and is very very cool. I can adjust the engine and atc audio levels seperatly from within FSX and as well the volume controls on the speakers and headsets. Lots of flexibility with this setup.So the question becomses, does anyone have any experience setting up RC so it only comes through a headset like the deafult FSX ATC can? If so, how? Thanks...Regards,