Although I have a Greyhawk 31DS not a Seneca, I tow a 2012 Ford Edge. I use a Blue Ox setup (baseplate and Aventa II towbar), light kit, and RViBrake2 for braking. Installation of the baseplate, wiring, and breakaway switch for the brake cast me about $1100 parts and labor. This price includes a 10" rise adapter for the towbar, as the Ford Edge has the connection points for the towbar at 26" above the ground, the highest of any vehicle my hitch guy has seen.
The towbar was about $700 several years ago, and the brake system was about $1100. All of them work very well as far as I am concerned, and I have towed for many thousands of miles.
2012 Greyhawk 31DS
2012 Ford Edge Toad
If I had anything better to do I would be doing it :)