I think I've been to 120 on one or two occasions. I'd never do it except on a straight, perfectly dry road with minimal traffic, in a full face helmet, a leather jacket, and heavy gloves.
Now, if you want to know the fastest I've been on a bicycle, I'm pretty sure that I went above 40 mph a few times, and my GPS shows me hitting 46 mph once, but that one might be a GPS glitch. I'm generally too chicken to pedal downhill, on account of having no real body protection. The fastest I went on anything resembling a flat road (not that we have many of those here) was 35 mph with a fierce tailwind.
With regard to the electric motor, I recommend that you check the laws in your state. Here in California any bicycle with an electric motor is legally restricted to 20 mph. A 1000W motor would be a huge overkill. It would be capable of pulling you at 20 mph up a 10% grade.