Problem is the data boxes on the E-series wasted a huge amount of screen real estate. I had an E-80 in the old boat and hated that.
What sort of setup does the boat have now? Because the data has to come from somewhere and if you're going to add a sender to provide the data you might want to consider a separate gauge just for rudder angle. I've got a basic analog version on my helm stations and I agree, it's very helpful to have it. There's also a separate one that feeds into my Simrad autopilot and it's not been nearly as reliable as the simpler analog unit.