What i am going to suggest it is not exactly matching what you have in your mind but i think it can cover your budget and ables you to gradually upgrade your dj hardware from simple to a bit more advanced.
On the first step you can buy the native instrument z1 which is 199 usd. This is a two channel mixer with built in sound card. It comes with traktor LE software. So with this you can start improving your transition and blending technics with real knobs and crossfader.
In the next step you can add up an x1 which also costs 199 usd and now you can work with fx via your controller. Also play cue and other playing commands are available on it.
The above setup works fine for two decks. But you still can play 4 decks via the traktor software.
