That's pretty much right at the top end of what you can get from a gigabit ethernet link. I'm not sure how you're getting 1143 on your laptop (unless the laptop and cable modem have got better than 1 gigabit network ports) but I would suspect it's not an accurate result. Rather than use a speedtest I would test using downloads, see if attaching the laptop directly still gives higher speeds.
Other than that, you can replace your current USB to ethernet adaptor to one with a Realtek chipset. From the testing done by dlakelan there's a significant drop in cpu usage when using an adapter using the RTL8153 chipset.