I need some advice on which gps unit to buy. My budget is R5000 and currently I am considering either the Garmin Edge 500 or the Edge 510. Is the difference in price worth it? I have read that the 510 has got quicker / better satelite connection and therefor more accurate. Are there any others that I should consider in this price range? in terms of functionality I want to see distance, speed, elevation and heart rate (maybe also power). It would be nice to be able to load a route / track or even to have navigation.Battery life is also improtant which is what eliminated the Polar M400 watch. Any advise would be appreciated.