You need these things why?
[link|http://www.pcdj.com/|pcdj] is 50 for the download of the basic version. With a single channel sound card you can mix but you can't cue (listen) to the next song.
SO, if you're looking to just smash songs together and play them through a big stereo...thats what you need. No other sound card (unless you want to cue, hot mix, etc.)