Thanks, sorphin.
I ended up switching to a different A+ switch port and the link negotiated to 1Gbps. As an aside, I was searching through the Windows System log and found the entry: ..."Gigabit Network Connection Smart Speed has downgraded the link speed from the maximum advertised." In doing some research found an Intel engineer who explains, "SmartSpeed is an algorithm that serves at link auto-negotiation where there is none. It tries to link at the highest speed, and if it can't, will downshift and try again. The purpose is to work around faulty equipment so you at least have link, instead of no link at all."
Don't know whether the port in question is bad and can't negotiate to 1Gbps or if it's something else. Seems to be just that port (switch port 4).
Transfer from NAS to PC from A+ switch port to switch port is now where it should be (80MB/sec).