At ISO 800, noise from the D7100 is a non-issue. I feel comfortable shooting this camera up to ISO3200 and will push it past that when need to be get the shot that I would otherwise miss. If it's a good capture, you can deal deal with High ISO noise in post.
What is a more relevant issue at higher ISO's is the loss of dynamic range. However, the DR of the D7100 is so broad at ISO100, that the losses at higher ISOs are still an improvement over an older camera at lower ISO.