Fast and powerful eh? Well, I own both the savage flux hp and the stampede 4x4. They are both respectably different trucks. One uses two batteries and one uses one. The savage flux hp is a 1/8 brushless beast. On 2x3s, it goes over 60+ mph stock. I have gps'ed it using my iPhone onboard. That speed is ultimately confirmed. However, the savage flux is not waterproof.The use of twin batteries are needed to run the truck. The portability of the truck is a big issue it weighs roughly 7kgs and is not a small truck.
The stampede 4x4 on the other hand feels different than the savage flux when driving. It is much lighter, 1/10 and uses one battery. It is also brushless but a much smaller brushless system having the least torque of the two. I have gps'ed it using the iPhone onboard at about 50+mph stock on 3s. That is pretty good. Looking at how light it is, if you hit a ramp at that speed, it will FLY.
It depends on what you do with it. For extreme bashing, just abusing the truck in everyday imaginable, the savage is right for you. For portability and just bashing with friends and occasional racing, the stampede is for you. I personally recommend the stampede if you are not into stripping the car apart and cleaning it because it is waterproof and you can literally bathe it in water (or mud hehe).
Hope this helps