Like almost everyone the bottleneck will be the internet connection you purchase.
The NAS unless it it part of the router would be better placed on the first gig switch even if that means moving it to another location. Still if the has gig ports it likely won't make a huge deal unless you have a nas that has RAID or SSD drives in it. Most consumer nas devices are well under 1g and some that use low power green drives are lucky to get 100m.