If a controller has an internal sound card it means that there's outputs for your speakers and your headphones, and sometimes more as you look at higher price points. If you bought a controller without a sound card built in, you'd have to either use your computer's headphone out or buy a sound card that supports two stereo outputs (such as the Audio 2). Personally, I'd go for the Mixtrack Pro. It's widely used for a reason. There's also the Mixtrack Pro 2 available for about $50-$100 more, which is essentially an updated version of the original. I'm not sure if it's sold in Australia yet but it runs off USB power only so there shouldn't be any compatibility issues if you buy it from overseas.