Not enough space on device when doing a Garmin map update

I have a Garmin nüvi 680 GPS which has 1.87GB capacity and an SD card with a 14.8GB capacity. When I go to do a map update using Garmin Express, it tells me I do not have enough space for the entire North America maps. I travel all over North America so it’s nice to have all the maps loaded. I have removed all these files to make space MP3, JPEG, All voices except one, all vehicles except one, but still not enough space.

I already have the gmapsupp.img (1,699.968 KB) file on the SD card. What other files can I safely move from the device to the SD card and not effect the operation of the device. Is it safe to move these large files to the SD card?
- Disk image files: gmapbmap.img (6,056 KB) and gmapprom.img (1,564,992) KB
- GCD file GUPDATE.GCD (10,382 KB).

Will these files just be replaced when I do an update?

Appreciate any advice from all you advanced users out there!