I think this isn't possible. You need two axis to plot x (one for the real part and one for the imaginary part - or the magnitude and the phase) and you need one axis for n1 and one for n2. Thus, you need four axis to plot, but we have only three.
You can create two 3d-plots: one with the real part of x versus n1 and n2 and one with the imaginary part of x versus n1 and n2.
Or you can use the magnitude and phase instead of the real and imaginary part, this depends on your needs.