We present an experimental investigation of our earlier theoretical predictions regarding the signal-to-noise ratio for magneto-optic readout from quadrilayer structures in a differential detection scheme. Using quadrilayer structures employing amorphous Tb-Fe alloys as the magnetic material, quartz as the dielectric material, and aluminum as the reflecting material, we show that the signal enhancement predicted for quadrilayers occurs even when the numerical aperture of the readout system is large, a crucial result for their effectiveness in magneto-optic storage applications. We also show that the signal-to-noise ratios measured are in quantitative agreement with theory.