Are you looking to use it as an actual sat nav, or just a radio/music player. I use my RNS-E as a music player with the SD card slots, one of the CD drives (older 6 CD changer doesn't work with it) and an AUX input and it works a treat. As far as using it as a sat nav, I'm far better off using my phone. My phones maps are constantly up to date and are as snappy as a sat nav. I've yet to ever be steered in the wrong direction by my phone.
As far as using it as a Nav unit, it might not be the best option considering you'll need to update the maps when available, and as far as I know, the updates are not free (unlike a phone).