Just noticed notebook check have benchmarks for the 850m and 860m
(select 650m, m750m, 850m, 860m then click restrict to get a comparison table)
http://www.notebookcheck.net/Mobile-Graphics-Cards-Benchmark-List.844.0.html
http://www.notebookcheck.net/NVIDIA-GeForce-GT-750M.90245.0.html
http://www.notebookcheck.net/NVIDIA-GeForce-GTX-850M.107795.0.html
http://www.notebookcheck.net/NVIDIA-GeForce-GTX-860M.107794.0.html
(select 650m, m750m, 850m, 860m then click restrict to get a comparison table)
http://www.notebookcheck.net/Mobile-Graphics-Cards-Benchmark-List.844.0.html
http://www.notebookcheck.net/NVIDIA-GeForce-GT-750M.90245.0.html
http://www.notebookcheck.net/NVIDIA-GeForce-GTX-850M.107795.0.html
http://www.notebookcheck.net/NVIDIA-GeForce-GTX-860M.107794.0.html