FYI, Tusq is just a fancy way of saying "polymer" which is a fancy way of saying plastic.
...No it isn't.
"A polymer is a large molecule (macromolecule) composed of repeating structural units. These subunits are typically connected by covalent chemical bonds. Although the term polymer is sometimes taken to refer to plastics, it actually encompasses a large class comprising both natural and synthetic materials with a wide variety of properties."
Here's a good video explaining what a nut is and does, properly.
At the end of the day, if you want more tuning stability, or if your at-the-nut action is too low, then you might want a new nut. If your guitar stays in tune already, and it probably does, as Ibanez tend to have straight string pull, then you probably won't see any significant change in your tone. or playability by getting a new nut.
That is, unless you're moving to an extreme. If you get a brass nut it will be brighter and sustain longer, a wooden nut, the exact opposite. Bone nuts are traditional, but as noted in the video, they're variable and there is good and bad. You can get a plastic nut that sounds better than a bone nut no problem, you just have to cut the plastic nut right and pick out a bone nut with a mediocre cut and soft leading edge.