I recently looked at the same. I ended up buying a second hand (but brand new condition, software never registered) Zumo 550 for �320 and I'm glad I did. I've heard a fair bit of negative comments on the 6-series and the 550 is really nice.

As far as software goes, I'm not sure if the Garmin software works on MAC (I gave up on MAC when Apple stopped make superior hardware), but I've used mine through Google Earth on Windows as well as Linux and that works really well.