Garmin Aera 500 is the dogs dangelers.
I have had it aver a week had a good play with the Aviation side on the grnd but not had chance to use it in the air
The auto side is great same as a nuvi, the bluetooth works real well with blackberry and even download the phonebook
sd allows music and audiobooks.
I would say the extra £400 or whatever it is for the 510 will not be worth it.
Any queries pm me if you want