Flight Sound X
A good friend bought this some time ago and it's has a very clear sound and voice for Vatsim etc. Very easy to install just plug the USB into your PC and you are up and running. It requires real pilot headset ! But it offers real intercom and very clear sound. It also have a external output so you can send the the sound to external speakers in the roof, just like in the real cockpit !
All input/output can be adjusted
I have bought two Telex airman 750, used versions. Just need to replace earpads..