As cyberjock already said, it depends on a number of factors, including the protocol used.
With CIFS, I'd expect to see speeds closer to 50 MB/sec. I have a N40L and see speeds in the 40's. Your CPU is 30% faster than mine.
My guess, is that performance would probably be worse if you added an SSD for caching (L2ARC). In general, they are used for specific use cases, where user's already have 32+Gb of RAM.