I was in the same situation a year ago.
Have Raymarine E120 (MFD).
Installed Raymarine EV400. Pump size was selected by Ram size.
My ram size allowed me to use a smaller pump or the larger one I installed.
I picked larger pump to allow better response in following sea.
On trials, powered up to 22 knots, on autopilot, perfect straight line.
Well designed system, Ray's forum is a nice resource:
(sounds like RayMarine is shutting the forum down)