I think it makes very little sense to discuss your future controller now. Also your choice of 4-channel controller. This is only really useful if you decide to hook up two other decks (be it through modular controllers, turntables, CD/Mediaplayers, etx.). The 4-deck option (switching decks between A/C and B/D) is not very useful for creative purposes, imho.
You seem to want to do a lot of different things. This tells me you have broad ambtitions and that your (expected/desired) workflow is not based on experience (yet). Some of the things you want (like work on your own tracks in a DAW) don’t really go well together. For Ableton use for example, you may find that other control surfaces are way more practical and useful than a DJ controller.
You mention getting a Traktor controller, which currently works best with Traktor software. The choice for software should not be dependent on the controller you want, but rather on the workflow you established. The choice of controller then follows as a result of workflow, chosen software and budget.
Getting a used starter controller is a good way to get your feet wet without breaking the bank. I’d certainly suggest spending some money on the How To Digital DJ Fast course, it is a real kick-starter in getting a good grasp of what goes into (controller) DJ-ing.
Frankly I’d stay away from the 4-channels in the beginning as you will be paying for things you won’t be using. Also the availability of 2-channel controllers is usually a lot better than for the 4-channels (as less people buy those).
Numark Mixtrack Pro 2 and 3, Reloop Beatmix 2, Pioneer DDJ-SB2 and Denon MC2000 make up our list of usual prospects. On the Traktor end of things (should you decide your workflow is best served by that software) it is the S2. Personally I would not invest in Behringer, Gemini or Hercules (although their latest flagships seems like a decent starter controller). Not to bash these brands, but there are considerably more negative experiences with those brands (either/or with product quality and service/support) than with the others. Individual cases may differ of course (people having problems with Reloop or Pioneer or working without problems for years on an el cheapo Hercules).
Go slow, practice each step til you feel you master it and build up your workflow to the point you know exactly what you want in software and controller features. The choice of your follow-up controller will be much clearer then.
Hope that helps some.
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