Carl,
if all your going to do if road stuff, then there plenty out there to chooe from een car based ones if you use a suitable case (IE the GIVI case).
The 60csx is a cracking bit of kit, but it doesn't do voice directions, it'll beep but no voices also you'll need to buy the mapping as well the 60csx is a GPS device that will basically put the dot on the road for what ever map you load onto it.
The Zumo and TomTom seem to get good reviews and they'll be about half the pric e of the BMW supplied GPS, actually I think the BMW unit is a rebadged Garmn Zumo.
HTH in some way