Absolutely you can. Install X2 first, then X3. I have X1, X2 and X3 on my DAW (all 64-bit versions) and they all co-exist just fine. They will not over-write each other. But because they share certain components, you want to install the oldest version first.
Oh, and by the way, because you have V-Vocal in X2, it will work in X3 just fine. Even though V-Vocal is not included with X3, the plumbing is all there so that it will work in X3 if you have it from a previous version of Sonar.