Originally Posted by
GrumpyDiver
Allan - the question may be down to what you are planning to do with the image that you capture. I'm starting to feel that you are overthinking this.
If you are planning to display them on a computer; I would not get too hung up on specific lenses, as the degree of enlargement will really not be an issue. If you are planning to make large prints, then you might start considering some higher end lenses; but smaller prints (anything up to say A3), you will be hard pressed to see significant difference in image quality between pro glass and amateur lenses if you are hand-holding your shots (which you have said you do). I do shoot a lot with a heavy-duty tripod and use pro glass, and yes, I can see a difference when I do large prints. In fact, I would suggest shooting with a tripod is going to do more for your image quality than anything else, but fully understand that this is not always a practical solution when on the road.
Software like Adobe Camera RAW or DxO Optics Pro do a wonderful job in correcting for lens "defects" (just make sure that the lens / camera combination you are looking at using are in their database). In normal lighting conditions, stop down a couple of stops and even the lower end lenses will give sparkling results. In poor lighting, often just getting the shot is going to be good.