Genuine RNS-E is a neat OEM-looking solution (wheel controls, DIS display) but the interface is clunky, navigation is really dated, you need add-ons for Bluetooth integration, it has no real phone integration or mirroring, no touch-screen etc. and they still make £200 or thereabouts.
There are various Chinese RNS-E-lookalikes available for similar money - both Windows and Android, and not all of them seem terrible. Only lack of DIS integration (which really isn't a big deal, I just like the idea of utilising it) really puts me off. You will need to research carefully though, as they're all superficially similar and some are clearly not of great quality.