The easiest way to do this is to call in and explain that you would like to upgrade the XG1v4 or the XG1v4-A. Availability is not gurranteed, and I cannot gurantee that this will work. The easiest way I have found to gain access to new equipment is to either contact @ComcastCares on twitter, or by simply having a tech visit. If you have a good technician they'll generally swap if you ask or if your having issues with your box. I would however, reccomend that you see this forum post: What is the Xfinity XG1v4 TV Box and how does it work? . You can post within the forum and request a XG1v4 self install kit. Again, keep in mind that these devices are not new, but are refurbs.
If you have any questions, you can either reply to me or I can tag a comcast employee. 🙂
Also, Welcome to the community!
I am not a Comcast Employee, I am a Community Member volunteering my time to help others.