I am a beginner DJ, and I am looking for my first set of equipment. I am doing a gig in a few months, and I am looking for equipment to use. It will be in a small room and there will be about 40 people there, if that matters. I have DJed before with another DJ, but he used CD players and I plan on becoming a digital DJ. I plan on using my computer, the software Mixxx, headphones, and Hercules DJ Control Mp3 e2, which is a MIDI controller. After some research I learned that I might need an audio interface. I found one called Numark DJ I/O Multi Channel USB 2.0 DJ Audio Interface. How do I know if I need to use this or not? Also, setting up a sound system has been very confusing to me. I am not sure what kind of speakers I need, if I need an amp, and what cables will be necessary. I also don't know whether the speakers will be connected to the MIDI controller or my computer. Any help or advice will be great. Please let me know if I am missing something, if the hardware I am using is correct, etc. Thanks!