Unfortunately, the X1C can not be upgraded to X1E using accessories.
The X1 and X1C printers do not support the installation of the chamber heating module and the wired network module.
Additionally, the X1 and X1C printers do not support installing the hotend assembly of the X1E (including the heater, NTC, and thermal grease).
That FAQ entry only mentions the chamber heater and wired network modules, as well as the hotend assembly. There is still hope for the air filtration module.