Hmm, most people here want stiffer suspensions, not softer ones.
Best bet is to change the tires to something with a soft sidewall. As you already have a GXE, you already have fairly small 16" wheels with high-profile sidewalls.. hmm... head on over to Tirerack and see if they have any tires listed in your stock size with a comfortable ride.
Naturally this only works if your tires on there now are pretty lousy.
Also, if you spend considerable time over rough pavement, the ride is going to be pretty choppy regardless of what you do, as the beam axle in the back just doesn't handle rough stuff well.