Windows Server 2008 R2 Slow LAN Transfer (Receive)

Question

Using Windows 7 Ultimate and Windows Server 2008 R2
Two machines, connected via 1GB 1000base-T LAN, with a 1Gb switch between... and yes, I've tried swapping cables and ports. Server has two RAID5's, a 6 platter and an 8 platter. Workstation has two RAID5's, a 3 SSD and a 4 platter. Both sides using Intel
CPU's and a RealTek 8100C chipset Gb LAN, same LAN drivers.
Using Windows Explorer to COPY a 20GB file:
Server Disk1 to Server Disk 2: >250MB/s (Server disk I/O isn't an issue).
Server Disk2 to Server Disk 1: >250MB/s (Server disk I/O isn't an issue).
Workstation Disk1 to Disk2: >150MB/s (Workstation disk I/O isn't an issue).
Workstation Disk2 to Disk1: >150MB/s (Workstation disk I/O isn't an issue).
Server Disk1 to Workstation Disk2: 91MB/s (near 100% LAN utilization).
All looks good so far:
Workstation Disk2 to Server Disk2: 25MB/s declining to 17MB/s; occasionally as low as 9MB/s. 
Some of the changes listed above appeared to work for a few moments. I've seen as high as 90MB/s for a few seconds, but it declines rapidly under 30MB/s... so no fix that has lasted. 
It appears there is something in Windows 7 that prevents fast transmits; or something in Windows Server 2008 that blocks fast receives. I have set the server-side receive training to disabled, normal, highlyrestricted, and experimental and the Win7 side
to off, normal, and highlyrestricted in various combinations. Again, nothing concrete to report as an improvement.
What would the MS Gurus suggest I do with NetMonitor as far as capturing something worth their time to diagnose?

Answer 1

I've tried disabling auto tuning on the clients with no appreciable effect. The throttling feature however appears to have had an effect - changing the setting from default 10 to 70 has slowed the transfer from 20MB/s down to about an initial 6MB/s that
has slowed even further, and is now at 3.2MB/s (3% network utilization according to Resource Monitor at both ends of the wire - WS2008R2 and W7).
Question: What does the 10 (0x0a and 70 (0x46) represent: Mbps on the LAN, or 10% and 70% reserved, or? 
I'll try the "off" setting of all FF's and add to this.
In any case, having a backup server that can't be utilized due to client "entertainment media" issues is a little painful... there should be a straightforward and published method to set the network to "normal".
UPDATE:
I've tried settings of 0, 10, 70, and FFFFFFFF. 10 might have been best, but only marginally better than 70. Range of time to copy was under 7 minutes to over 8 minutes. Very small difference.
But I also tried this using Windows Explorer and a Dataset of one folder containing 12.5GB of miscellaneous folders and files - and was surprised.
 - Dataset is at \\WIN7\Dx\ = = Client physical RAID5 drive D:\Dataset
On WIN7 Client: Share drive D with Everyone as Dx
On WSvr Server: Share drive D with Everyone as Dx
On WIN7 Client: Map \\WSvr\Dx to Z:
On WSvr Server: Map \\WIN7\Dx  to Z:
On WIN7 Client, using Windows Explorer:
 -- Copy Dataset from Local Drive D: to Network Drive Z:
 -- Took about  8 minutes, with 20% network utilization.
On WSvr (2008 R2 Server), using Windows Explorer:
 -- Copy Dataset from Network Drive Z: to Local Drive D:
 -- Took about 3 minutes, and 70% network utilization.
Why does running the copy from the server allow better network utilization and net throughput?
UPDATE2: 
I am NOT using HOMEGROUP; I have a dedicated workgroup network the client is a member of, and the server is a DC. I'll eventually try joining the client to the domain and see if that changes anything, but doubt it will so haven't taken the time yet.