I think the problem here is that you assume focal length is all (or the most important factor) you need to look at when choosing a new lens. It isn't. Your other problem is assuming that a lens is going to solve your problems. It may not.
All things being equal, getting a walkaround superzoom when you already have a "twin kit" of a wide-to-normal/short telephoto zoom and a telephoto zoom is only really going to be worth it if you can afford it, and a) the "breakover" point between your existing two lenses (in this case 55mm) is particularly awkward for your personal preferences on framing and working distances, b) you just really really hate changing lenses, or c) you really have to travel light (e.g., travel kit).
You typically aren't going to get a great improvement in image quality or any additional low-light capability, since all of these lenses are liable to have relatively slow maximum apertures (typically f/4-5.6). For indoor shots without a flash, you probably want a lens with a larger maximum aperture so you can either use a lower ISO setting or a faster shutter speed and still get a good exposure vs. your "slower" lenses. Or, you may want to get a flash or tripod instead.
If you think that stabilizing your camera (for stationary subjects) or adding light into the scene aren't the answers, and you're determined to get a lens, then what you're probably looking for is a maximum aperture of f/2.8 or larger. With zooms, f/2.8 is liable to be your maximum (unless you shoot Olympus), and can get expensive. With primes, you can get much faster for lower cost, but you won't have the versatility of a variable focal length, and will need to know approximately what focal length you prefer.
This is just me, but consider what it is you really want this lens to do. dSLR lenses tend to work better as special-purpose tools. Having a walkaround zoom and then getting another walkaround zoom is kind of like looking in your toolbox which only has a hammer in it, and deciding what you really need is a better hammer. When maybe what you really need is a screwdriver, a tape measure, or a wrench. Not everything is a nail. :) Consider the other possible tools you could buy and whether they might be a better fit than the tool you already know.