Touring/Touring+
or 1000 if you're feeling particularly flush.
Yup - all three have maps on board (Garmin's maps, based on Open Cyclemap). The 800/810 can be used like this, but you need to load Opencyclemap/Openstreet map on a micro SD card which you then use in the device (it will cost you a fiver or so for the card, and a little bit of time downloading and unpacking the files). FWIW, the 800 performance bundle is £223 at
Wiggle at the moment (includes HRM and Cadence/speed sensor).
Velogps have some videos of the "breadcrumb trail" navigation you can use on the 200/500/510 online.
AFAIK, only the touring/touring + offer a "give me a circular ride of x distance from here" option, but I don't know the spec of the 1000, beyond knowing that it has the Garmin cycling maps bundled.