Well, the 2002x is one of the only mixers from Numark I've never used, but I've heard it's pretty good for it's price range, so I guess you can go for it.
About the EQ, basically they all work the same way, but there are some slight differences.
Ok, we're talking about dj mixers here : most of those have 3-band EQ, this means you can control treble(high tones, hihats and such), midtones (vocals and the "kick of the bass" are part of this) and bass(low tones). Basically the cutoff frequencies are : 100 Hz for low, 1 kHz for mid and 10 kHz for high. Some more expensive mixers (like
Xone 464 and 62) have more bands, they have finer control (for example with Xone you have highmids and lowmids).
A basic EQ can attenuate or boost the specified frequency. The degree of attenuation/boost is measured by dB (decibel). Just know that every change of 3 dB equals a doubling or halving of the sound level on that frequency. (Maybe you learned in physics that if you have a certain sound let's say at 80 dB, and you put and identical source next to it, the resulting level won't be
160 dB, but 83, so double level = +3 dB).
Most of the basic EQ have +/-10, +/-12, +/-15 dB control. With those levels you won't be able to completely remove the specific frequency?
That's why kills came on the market. In theory kills let you completely remove a certain frequency (in theory, cuz of the construction of the circuitry it's not always that way). You have two sorts of kills : kill switches (two positions : kill on/off) and rotary kills (same as the normal rotary knob EQ's, but the attenuation goes further : from -24 dB up to -60 dB on some mixers). In normal use, if you kill a certain frequency, you won't hear it anymore, because the other frequencies will sound over it. You'll still hear it if only that frequency plays, but that doesn't happen often.
But there's another parameter. The EQ doesn't cut exactly that specific frequency, but also adjacent frequencies (for example bass : you won't only cut 100 Hz, but also some of 150 Hz, 200 Hz, etc.). If you put this on a graph (sorry don't have one right now, it's on the way), you'll see that there is a slope with a maximum on the chosen frequency. The rate of that slope is called Q (from quality). On low budget mixers, that slope is pretty flat, which means they will attenuate/boost a lot of the adjacent frequencies.
Better (read more expensive) mixers have a higher Q (steeper slope) so they work more precisely around that frequency. The problem is that dj mixers have a predefined Q on their EQ (budget reasons). Expensive studio/stage mixers have adjustable Q on their EQ.
A high Q also helps a lot on the quality of the EQ in that way you don't need that much cut range to have a convincing result.
For example, I'm going to buy a Rodec mixer. In my opinion it has the best EQ of all dj mixers in the world (and god knows I had a lot in my hands). It has an extremely high Q on the EQ's, so if for example you cut the bass, the midtones are not touched. For that reason, Rodec doesn't use kills!!! Their EQ's have a +/- 13 dB range only, and it's enough.
Hope I've helped
