A 166 is fucken monster sized for your weight.
I'm about your size, wear size 11s, weight slightly more than you, and my Hot Knife is 158. And I wouldn't consider going bigger than that, unless you're going to be riding in pure pow.
Side question: If you're use to hard boots, why not get stiffer bindings and boots?
Wow. No doubt. A 166 is fucking HUGE. I weigh nearly 20 pounds more than the TS and my biggest board is my 164 Charlie Slasher pow stick and that thing is all I'd care to try to throw around in the trees. I rode killclimbz old 169 NS Premier splitboard once and it was WAY too much board for me.