Absent running a "Trophy Truck" suspension, no shock adjustable or not is going to soften the washboard ride. Your only real solution(absent very deep pockets) is to pick up a good set of shocks that are more street biased(since that is where you spend most of your time), a 12volt comnpressor and storage tank(under $100 at Pepboys )and lower the psi to 12-15 depending on the type of tire you are running. The lower psi allows the sidewalls of the tire to absorb the bumps instead of the shocks, reducing the effects of thewashboards. I run my AT's at 15, and my MT's at 12. With these psi's I get as smooth of a ride as when I am on the highway, whether going slow behind trailered traffic or wide open on a long straight away "Ivan Stewart" style.

With speed the main thing is being able to slow down in time, which is a lot easier when running a lower psi. I usually always run in 4low when aired down, the higher drive ratio allows for good engine breaking, and 4wd allows for better traction.