Oh, and now I think of it, unless you've got a grand or two to spare you're always going to be compromising on lots to get a wide focal length range. Which is why SLRs have changable lenses!
You might be better off looking for a better replacement for your 55-200 if you are not happy with its performance. I've just bought a 28-105 USM as a walk about lens, much better quality than the 18-55 and 70-300 but still nowhere near L glass sharpness (but then nowhere near L glass price either!)
