Since all EQs do basically the same (raise the volume in some frequency bands and lower them in some others), I would strongly discourage using several of them in parallel. While it won't degrade the quality of you recording, it's just counterintuitive: Each of the EQs tells you it does somthing very specific, while another one in the background does just the opposite.
Which one you use is pretty much a matter of taste: The Graphic EQ is good for getting an overall picture of how the frequencies are treated. You can give it a nice "wave" shape. Also, you can use it to single out a "bad" frequency that you don't want, like a resonance or even a hum in some narrow band, and lower its volume.
However, the parametric EQ is better suited to do the latter – you can pick the exact frequency and determine how "steep" the curve is to the left and right of it (with the "Q" parameter).
The Visual EQ is kind of a combination of both - it's a 4-band parametric equalizer (without "Q" parameters). You pick the 4 frequencies you want to affect and their respective gain values. The fun thing is the interactive graphic interface which shows you how the overall spectrum is affected, so you don't have to enter values numerically. And the "Analyzer" shows you immediately how your track's frequency spectrum is affected.
As I said, it's a matter of taste, I've come to like the Visual EQ more and more.
