I would like to install a whole house transfer switch. The current setup is a 100a main disconnect (with fuses)connected via a 2 in. stub out the side to a breaker panel. I was thinking I could remove the wires from the bottom of the disconnect. Install a transfer switch below the main disconnect. Run new wire from disconnect down into the transfer switch and up to connect to the wires removed from the disconnect.

What size wire should I be using? Do I need split bolts to connect or are the big blue wire nuts OK?
What brand of transfer switches does anyone here reccommend? What price ranges exist?
I live in Ontario Canada.