JB Systems offer the affordable BATTLE4-USB DJ mixer for scratchers jut starting out. It's equipped with the necessary analogue inputs as well as two USB ports so you can connect it directly to your computer. It will detect the mixer as an audio interface via the software, and even if you've got a pair of turntables plugged in, you can still use it. Another cool feature of the BATTLE4-USB is that you can organise three channels: set channel 1 to the X crossfader, channel 2 to the Y and 3 to master. Now you can use the crossfader to mix your tracks and have them flow together harmoniously.