One problem will be the time the gps takes to read the SD card if it's full of tunes. IIRC the limit for tunes is bypassed by putting the tunes into folders. Got a 4 gb disk in mine.
Also depends what you want to put on the card, cos the Zumo's limited to 1,000 music tracks (unless you rip the album as one continuous track - then you can have as many albums as the SD card will take, up to the 1,000 limit)
Also depends what you want to put on the card, cos the Zumo's limited to 1,000 music tracks (unless you rip the album as one continuous track - then you can have as many albums as the SD card will take, up to the 1,000 limit)
Garmin suggest that you use up to 4gb sdhc. Although as already mentioned it can take bigger but you will see slowness in reading and reloading of certain pages. Go for a 4gb that should do you fine.