@HelsBells Cambs since I am not rich and my Edge 500 was stolen (no not outside at home), I ended up with a edge 705 from
ebay for £45, a new battery and mount (got a sram quarter turn out front mount an adaptor the 705 isn't a quarter turn by default) found out which firmwear worked best, it was good to go, I already had cad/sp hrm monitors.
It takes either tcx course files or gpx files for navigation, it can work out routes if need be, but I usually know where I am going if local, and future a field the route is planned usually with the course as I can use the vp thingy (usually get beat though) as for speed its nice to see (usually depressing though) but I tend to watch my cad more than speed, time to way points crs end eta ect have there uses, host of other stuff too.
The reason I went with a 705 apart from cost was the open file structure of tcx and gpx files.