For those who are confused about the Stealthplug, you need to understand that StealthPlug is a miniature soundcard / audio interface and hence it runs independently of whatever soundcard is already installed on your PC. So all input AND output is routed through the StealthPlug once your software has selected to use it. It uses the high-speed ASIO driver system which has no connection with Windows own, built-in and inefficient, DirectX system, You need to use ASIO drivers because the DirectX drivers are too slow and you would get delay when you played your guitar (latency). As the StealthPlug is a separate soundcard, it needs to be connected to speakers directly (or to headphones) using the small socket on the side. It does not use the computer's own speakers because these already connected to the computers built-in sound card. Mac machines let you play with the audio card settings through the Mac control panel so you don't have to worry about separate drivers.
It is a great little device and is easy to set up and configure. It gives you a high quality, low latency connection for your guitar, so you can completely forget about the poorer sound system supplied in most PCs (especially laptops!).