I finally found the right saddle/saddle position to avoid numbness, after only about 4 years on this bike. I might still do some tweaking to the position as I do longer rides. It's often not just the saddle, so do be sure to check the rest of your position. Find a fit machine if you haven't already, or use wrenchscience or something similar as a guide (don't take their numbers for truth, just a guide).

But, the Fizik Aliante is pretty comfy for my bum.