If you happen to have found this page as a former Sunrocket customer, here is a way you can get a phone up and running quickly. One potential VOIP provider you can use is Viatalk. This is the one I chose. Sign up for BYOD service. Wait unil you get your e-mail from ViaTalk with your login information. It took me less than a day to get mine even without paying for rush processing. I have an Innomedia gizmo. If you have one of the others, these instructions won't work for you. Here are the instructions I followed to get my gizmo to work with ViaTalk.
These instructions were taken largely from this thread by Skruffy on SunrocketForum.
If you know of similar instructions for the Linksys or AC-211, please post links in the comments.