I have a mbp 2.4ghz, santa rosa model. I want to start off as a dj. Is there any simple mac dj'jing app for the mac which i can use as a newbie and one which will also help me learn! Can I dj without any external hardware when I start off? If i should need to buy an external sound card later, which one should i buy? Creative Sound Blaster X-Fi Xtreme Audio?