Reply to soundcard help/questions

My setup consists of a numark mixtrack pro and a novation launchpad. As I said in one of my previous threads, my computer kept freezing when I plug in my launchpad. Ive been using the mixtrack pro soundcard but one day I switched the soundcard to the computer soundcard and it does not freeze up as bad. I am wondering if there is something about soundcards that I should know. Im also looking at getting the audio 2 dj as my new soundcard so give me your input on this please!