Those are certainly some

Those are certainly some pathetic speeds. I easily hit 800 Mbps+ on WHS 2011 with essentially nothing other than a default config, consumer-grade GigE switches and Intel NICs.

First step: Update ALL of your drivers to the latest including BIOS. Use the manufacturer drivers and not those from Windows Update. Do this on both client and server.

Second Step: Try a transfer bypassing your Linksys. Verify you can get a decent transfer speed directly connected.

Third Step: Add the Linksys back and try again. Honestly, it is worth buying a GigE switch for the type of transfers you are doing. I have had good luck with this very reasonably priced D-Link switch. Wireless file transfers are going to be slow no matter what. If you are intent on doing them, consider upgrading to a Wireless-N solution.