From your comments, I guessed that your problem are artefacts of an automatic vectorisation. These can be reduced by playing with the parameters of the tracer, but it is unlikely that this suffices to make the final images better than an automatically scaled bitmap.
To make use of the advantages of the SVG (or any other vector format), you have to correct the result of the tracer by hand. E.g., in your third example picture, you could make the following improvements (I recommend to start with this, since it is by far the most simple image):
- Use actual rectangles for the rectangles by using Inkscape’s rectangle objects or using a Path object that only consists of four appropriately placed vertices connected with straight lines.
- Use an actual circle objects for the circles.
- Ensure that every line that should be straight actually is, e.g., all the lines that are not at the end of a stroke in the big T.
- Use the original logo font or at least some very similar font for the word series. (And yes, the font may be very difficult or impossible to find.)
Of course it might also help to have a high-resolution bitmap to trace from.