I'd only stick with VW if you want to keep everything OEM.
The RNS510 is limited in what it can do compared to what some of the latest head units can do.
What the RNS can't do:
Play any video other than just DVD-Video
Play anything other than MP3 and WMA eg AAC, OGG
Show images, album art etc
No built-in bluetooth capability
No support for iphone/ipods without extra cables eg MDI interface
And the satnav isn't the fastest or the best.
But it's fine for my needs and it's OEM, which for me is important.