126mm for a 6 speed is better than keeping at 120mm and using an ultra 6?

I think I want a new 165 crank - I hear they're smoother, and I'm 5'7" w/ a bad r knee.

Also, Also I need "long reach" brakes for 700c wheels, as I'm not planning on rebasing the rear brake bridge, or getting a new front fork. Any knowledge out there if these would be long enough?