Reply to Video Mixing

I was curious to how this can be done with a stand alone mixer without any DVS. I'm basically working with two CDJ900s and a DJM 800. I have a decent laptop that I solely use for browsing and RekordBox.

So my question is:
What wire/connections/hardware/programs would I need to make a nice fluid video show? I hear that an external sound card may be needed and a nice visualization program can be bought.