I fitted the Raymarine Evolution autopilot system with the direct drive motor to my 2002 B32 ‘Another Fantasy’ some years ago, replacing the original ST60 wheel system. It’s much more responsive than the wheel drive of the ST60; much quicker response and easily copes with rough weather. It requires a mounting plate to be glassed in to the interior space in the transom aft of the aft cabin to enable the direct drive motor to be mounted and connected to the rudder quadrant. I had the job done professionally but it’s certainly possible to DIY if you have the requisite skills. As you say, it’s expensive but well worth it in terms of vastly improved autopilot performance.
Hope this helps….