Microphone and Speaker set up for Vatsim

I would really like some help/advice in respect of the following;

I have registered with Vatsim and will shortly download the software required.

Once it is all in placed and installed I would like to play the sounds of the aircraft through my Corsair twin speakers and the Vatsim ATC through my Razer Carcharius Headphones which has the Xonar U3  soundcard adapter.

I will also be using FS2 Crew and flying the 737 NGX.

Can someone advise me how I set it up in order that I can have sounds out of the speakers for the aircraft sounds and the headphones for Vatsim ATC.

Many thanks in anticipation.

I am running on Windows 7.

Michael