Digger,
Chivita, our 22' cruiser, has the Baystar system and an Sportpilot plus which works pretty well. An option you might consider that is substancially cheaper than going with the SeaStar system with dual helms is going instead with a remote control for the autopilot. It will not control your speed, but it will control the helm. With only 50 hours on Chivita, I'm still learning her personality and I'm not yet comfortable with connecting my remote and steering from the cockpit, roof or where ever so I cannot say how well it will work. My father's boats on the other hand all have this setup and he swears by it. I have used the remotes on his boats and they have worked very well, sitting on the forward deck of his houseboat with nothing but open water in front of you and steering all over a lake with the remote is absolute paradise. Really puzzles people since they can't figure out who is steering the thing.
Two other comments/thoughts I have on what you are contemplating, instead of the Sportpilot plus, if you have the funds, I'd heavily recommend talking to Les about the ST5000. It seems to be a stronger system and there are more accesories available for it, Les has alot of experience with it and can give you more detail. Also, not sure which engine(s) you have, but my father and I have just discovered that the 40 horse Yamaha's cannot use a Baystar or Seastar without some serious modifications to the transom mount. There are two tabs on the Yamaha 40 that allow you to mount it with screw down bolts to the front of the transom. These have to be cut off if you want to be able tilt the engine up with the Baystar/Seastar hydralic ram mounted to it or you will bend the Baystar/Seastar cylinder.
Chivita Dave