Have you considered putting the E80 at the
helm, since it's already designed for outdoor use, and running an ethernet cable from a
Seatalk HS
network switch (which you probably already have, if you have several devices feeding your E-80) to the nav station, where you can use a
laptop PC. If you are getting
radar,
AIS,
GPS at the E80, you should be able to also display these at the helm.
I haven't used Raymarine's Raytech
software, but according to their website it's fully compatible with the E series.
Raymarine Marine Electronics - RayTech RNS v6.1 (Full Version)
It looks expensive, but may be cheaper than another display from Raymarine.