What network throughput is possible with WS9 + 10GbE?

I'm getting approximately 325 Mbits/sec throughput with Iperf on VM-network-VM (same host) tests without any tuning whatsoever.  I know that's very slow but what would be considered an achievable result given my setup (see below)?

Host:  Win 7/Workstation 9/E5620/24 GB Ram/10 GbE

VMs:  Win 7/3 Gb RAM

bin/iperf.exe -c 192.168.2.4 -P 1 -i 1 -p 5001 -f m -t 10

------------------------------------------------------------

Client connecting to 192.168.2.4, TCP port 5001

TCP window size: 0.01 MByte (default)

------------------------------------------------------------

[128] local 192.168.2.3 port 49167 connected with 192.168.2.4 port 5001

[ ID] Interval       Transfer     Bandwidth

[128]  0.0- 1.0 sec  43.7 MBytes   367 Mbits/sec

[128]  1.0- 2.0 sec  38.3 MBytes   321 Mbits/sec

[128]  2.0- 3.0 sec  38.5 MBytes   323 Mbits/sec

[128]  3.0- 4.0 sec  37.1 MBytes   311 Mbits/sec

[128]  4.0- 5.0 sec  38.9 MBytes   326 Mbits/sec

[128]  5.0- 6.0 sec  38.6 MBytes   323 Mbits/sec

[128]  6.0- 7.0 sec  40.2 MBytes   337 Mbits/sec

[128]  7.0- 8.0 sec  38.8 MBytes   325 Mbits/sec

[128]  8.0- 9.0 sec  38.2 MBytes   320 Mbits/sec

[128]  9.0-10.0 sec  37.0 MBytes   310 Mbits/sec

[128]  0.0-10.0 sec   389 MBytes   326 Mbits/sec

Done.

John Treble

Ottawa, Canada