Go to your music/DJ store, see if you can get hands on the products, see how they react, feel, what software you feel comfortable using. Don’t get drawn into the ‘industry standard’ speak.
There are different types of controller, all in one, which provide all the necessary buttons, encoders and sliders for basic and intermediate DJ use. (2 deck one mixer configuration) and normally have a soundcard built in, ready to connect to sound system.
Then ya got the modular setups, which consist of different controllers, all shapes, makes and sizes, that deal with basic DJ functions, right up to the dizzy heights of what the software allows, and you’ll see setups where DJ’s have a few different controllers for different aspects of the control of the software, a good example of this (but not exclusive to) is DJ’ing with Ableton. You will need a sound interface (external soundcard) for these types. Some examples, Novation Control XL, NI Kontrol X1, Novation Launchpad, AKAI APC40 (production tool, but can be used for DJ’ing too) Midi fighter Twister, google these to find out more info..
You want to scratch, you gonna need something with decent jog wheels, most reviews should cover this.
You may be surprised to realise that the software will play a big part in this. The traktor controllers are configured for traktor software, and other controllers may be affiliated to other progs such as serato, offering an easy to operate out of the box scenario. It’s something you will have to consider. Denon for example push the Serato thing, as does pioneer, and depending on offers or spec, will give you a full version of serato, but these controllers are awesome when mapped to Traktor.
In respect of the “all in ones” Controller ‘accessories’ don’t really exist, they are generally designed to be used as an all in one dj solution when hooked into a computer/laptop, and most now don’t have soundcard issues, they are generally built in now (unless you go modular) A lower specced controller may hamper your creativity down the line. But easy to overcome, you’ll either upgrade, or buy something to enhance your existing setup. For example, I use a Novation Launchpad with my Denon 6KMk2 for advanced Traktor controls.
As for headphones, that’s your call, those Audio Technica are pretty good cans and I personally don’t see a problem, with you using them, but the problem with em from a DJ angle, is that they are studio monitors, and with the very nature of DJ’ing being very harsh on headphones, don’t be surprised if they become damaged. Most DJ headphones are hinged, are slightly more flexible and are designed to be a bit more robust than your normal listen at home/studio types.
A lot of DJ’s swear by Sennheiser HD25, I personally use Denon HP-700, upgraded from Sony MDR700, and I can’t complain..