If you are not using the Command Center, and you continue to struggle with downloading, you might want to consider temporarily suspending your antivirus software during the download. Everything can be scanned after it finishes downloading, and that should make the download process a lot quicker.
Additionally, you could - and lots of folks with slower internet download speeds do - consider using a download manager for doing the Sonar download - making sure the one you choose supports a restart or resume function, so you can pick it back up if you time out in the download process. (I think you can do this with the new release - don't know about if you use the Command Center)