I'm certainly no expert so don't take this as gospel but if it were me I would go with the bigger motors. 166 sounds a little small and I'd rather be overpowered than underpowered. Forty five bucks isn't much difference and you'll be money ahead if it turned out the 166's couldn't handle the load. On the other hand you might do some tests to determine just what your torque requirements are. I haven't seen a lot of builds with 166's but that doesn't mean they won't work.