Backup performance to network share

I've read the related performance posts, but found nothing that talked about what I'm seeing, which is unexplainable poor performance backing up to a network share on a home network. Windows 7 64Bit systems, gigabit router and cards for all. I've setup a network share that I'm doing the first full backup to. I have several tools that show me network throughput performance. When I just copy a large file from System A to the shared folder on System B, I see 800-900Mbit/s performance. Acronis maxes out at about 66Mbit/s. Performance options set to Normal compression, no limit on transfer speeds. Can't figure out what else to tweak. Any suggestions will be appreciated.