Hi, for sure the C-version will take the update. I'll recommend you to update the unit, with 1 risk: there's no way for roll back at this time, maybe in the future. The unit with the US firmware is much better then the EU with modified disc, but it depends on what you really want. Check this forum for the pro's and contra's of a real US unit (pro: satelllite radio, contra: disclaimer always by start up, etc..). When you update the unit, you can't use your modified disc anymore, you'll need the real US disc.