Speaking completely from my own point of view:
I would invest in a decent DVS (I presume you already have a laptop to run it on) and use your Numark decks to get cracking. DVS software these days have bpm counters and phase meters to help you learn to mix with, so the learning curve with DVS is far gentler than when I first started on just vinyl.
On the other hand, you can get a decent controller for about the same money as a DVS, and they usually have a shorter learning investment, so don’t discount that option totally either. Plus controllers are less hassle to lug around once you start gigging. I take my technics decks, my mixer, my laptop and my DVS to gigs with me. Its a pain but I just prefer using vinyl to control my music.
.
