I have an RCD510, touch screen radio and 6 disc CD player. It's not DAB and doesn't have sat nav, but I've got a hard drive plugged into the USB port in the car and got all my music on there and can access it through the touch screen. I like it, think i paid £150 for it quite a few years back.
As
R3k1355 stated, make sure you get a code. However mine didn't, and all the dealer needs is a number off of the unit somewhere and they put it in their computer and it returns a security key; it's practically instantaneous and borderline criminal that the dealers can charge you for it.