To directly answer the original post...you do not need a mechanically powered sharpening system to sharpen your knife. Although, powered sharpeners used properly can be very fast in delivering a very sharp edge. A few seconds on a belt sander/grinder could equal a few hours on a stone.
There are some thoughts to consider: 1. How portable does your system need to be for your sharpening needs? 2. How often will you be returning to your sharpening system? 3. How much time do you have to invest in learning and using a sharpening setup? 4. How much money are you willing to invest in your sharpening setup?
I have a 72"x2" belt grinder from Grizzly, multiple 1"x30" belt grinders from Grizzly and Harbor Freight, Three setups of Paper Wheels (yes one is a cheap version and no it does not work as well as the proper ones sold at Grizzly and other stores), multiple Spyderco Sharpmakers, a Lansky Crock Stick, Spyderco bench stones, hardware store bench stones, pocket stones that I actually carry everyday at work, and loads of automotive sandpaper. All of these things can be used to sharpen knives and I can achieve very good results will all of them because I sharpen a lot of knives per year. The most important part of getting the most out of your setup is to practice with what you have and observe what shortcomings are present.
For example in your original post, you mention using "a waterstone" and that you are not seeing results. Is the issue you are facing that your one waterstone is too fine an abrasive to remove enough material in a reasonable amount of time, or is it too coarse and you are lacking edge refinement? Have you read any posts about the Sharpie trick? This trick will give you some insight into your sharpening issue. It will show you if you are sharpening at the edge or hitting the shoulder (above the edge at which point you are reprofiling the edge which is not always a bad thing if that is your goal). As mentioned before there are lots of great threads and videos on the topic of sharpening.
Give us a little more information about your current setup and details on the knife/knives you are sharpening and you will have much more relivant replies to read.
Good for you for asking the questions, it is the begining of the road to the solution!
Best wishes to you.
Doug