Your 700 had a 2.5GB hard drive, and I should imagine that you'll need to switch to a 'zoned' map now (you can't fit it all on there at once!), but the most current zoned map of Europe that lets you load half or more at a time (current version is 925 - a very long ways from 660!) should still work on your unit. TomTom has been very good about finding ways to keep even their oldest units updated with new maps, even in the face of increasing map size and some older units that were a bit skinny on memory.
7.903 was the last firmware released for the 700.