It could still be your rotors. I had a 2006 and if I over-tightened my lug nuts the rotor would warp enough to cause shaking during braking. That said, it only did it during braking and not during acceleration, cruising, or coasting.
As yours does it at a specific speed and during braking, I'd suggest investigation your balancing in addition to general suspension inspection. During braking any balance issues will be greatly exaggerated while various amounts of balance issues will be accentuated at certain speeds whenever the amount of out-of-balance wobble matches the rotation of the wheel at a given speed.