Thanks rhino123, daredevil123, crabballfor ur advice =),..so u mean that the larger the zoom range the IQ will be affected?
Short answer: yes.
Long answer: Depends.
In short the larger the zoom, the more optic elements are in the lens and that will cause the following issues
1) Light lost (will affect speed of the lens, sharpness, etc)
2) Distortion
However this might not be the case (or at least not as pronounce) if the lens are designed properly. But that would also mean that the lens would be larger and more expensive.
You need to weigh in the disadvantage and advantages of a lens with large zoom. For alot of people, the lost in IQ was not really that important when compared to the flexibility of the lens and it really don't show if you are not printing 100% crop and only go for small print.
Canon had a 18-200mm lens available as kit too, and there is a CS brother here who uses this lens to its fullest capability and I tell you, the result is excellent.
You could also looked into the following combination,
Canon 100D or Nikon D5300 with 18-55mm kit lens + 55-250mm STM lens (for Canon) or 55-200mm (For Nikon)
This shouldn't set you back too much. But you do have to change lens quite frequently depending on what you intent to shoot.
Another way is to get the body only and get a Sigma 17-70mm lens. I have one - the older version (I am thinking the newer one should be better), and this lens is on my 7D most of the time. It is not excellent but it serve its purpose.