I currently have a d5000. 2 kit lenses 18-55 and 70-200. I recently purchased 1.8 50mm, and sigma 2.8 24-70 lense. I primarly shoot dogs stationary and in movement. I also like to do landscapes and portraits. I did purchase a d600 refurbished and first pic testing had over 12 oil spots. I returned it, and found out about the d610. I want to purchase the Nikon 2.8 70-200 lense as well. the difference is almost 1,000.00 between d7100 and d610. the Nikon 2.8 70-200 will be around 2300.00. is there going to be that much difference with the d610 vs the d7100. I have just started being asked to do photos for people and consider this a serious hobby doing photos most everyday. Thanks for any suggestions.