I've done exactly this myself - Evolution brains and Pelagic actuator. It's new this season and I've only had one day testing it but it steers well, doesn't hunt with waves like the old ST2000 and is SO quiet in comparison. One thing did annoy me though, if she became hard pressed and the actuator reached full travel without any change in course not only did it raise the usual alarm but it stopped trying to steer which leaves you with a decent amount of tiller locked on. The ST2000 doesn't do that, it just recovers and carries on.
EDIT: You need the control head as well which is £500 by itself.
I believe the Pelagic actuator is available much more cheaply from other sources as previously mentioned.