I purchased a D7000 with the 18-200mm lens and and very happy with it in most situations. At 200mm it's a bit soft and I've seen a little bit of vignetting in the corners.
I am heading to Costa Rica in May and anticipate needing more reach to shoot wildlife. There is also high probability of low lighting situations in the jungle. I don't have the budget of a professional photographer. I originally thought to buy the Kenko Pro 300 1.4X teleconverter, but after much research learned that it's not a good match for my existing lens.
All that said, can anyone recommend a good, affordable option? I'd like to spend about $500, but it almost seems impossible for what I need to get out of a lens. So I can go as high as $1000. Thinking maybe a stronger telephoto lens and possibly add the teleconverter? Or looking for a used, better piece of glass? Or of course, there are the off brands (which I don't know much about). I'd appreciate any suggestions on both the glass and where to purchase it at a savings.