compatible modems

I just signed up for the ultimate tier and noticed that my current netgear CMD31T modem is not on the compatible list for that speed. The technician is coming tomorrow to get everything set up and I'm just curious if it will work until I can upgrade. Having a lower speed for a short while won't be an issue as I doubt it will be slower than what I'm getting now through att.

Also on that note are the modems that are listed the only ones that will work with cox or if I find something off list can I use that? Thanks in advance!