There are two variants of Nokia X6-00: RM-559 (this report) and RM-551 (different hardware configuration, often with 16GB storage and microSD support). Firmware for RM-559 is not compatible with RM-551.
The firmware isn't just one file; it's a collection of parts that tell the phone how to behave. For the , you look for: : The core operating system. firmware-nokia-x6-00-rm-559
Several firmware updates were released for the Nokia X6-00 (RM-559), including: There are two variants of Nokia X6-00: RM-559
You're looking for information on the firmware for the Nokia X6-00 (RM-559). firmware-nokia-x6-00-rm-559