RNS510 is nice looking but I don't like how slow it is and the power output is silly. Also I needed a Bluetooth module for mine and wasn't prepared to pay the silly money for one and the microphone, then the hassle of fitting and coding it...
I had a Kenwood DNX520VBT (like above) in my last ED30 and wasn't a huge fan. It was old and felt old, bluetooth doesn't do audio streaming either.
I also used a Kenwood DDX-4025DAB. That was ok apart from the screen was way too dim and you couldn't see it.
This time I have just fitted a Pioneer AVH-X2700BT and I really like it. The customisation options for both the looks and sound are great, and its really smooth and easy to use. The sound quality is great with standard speakers too and the screen can actually be seen. It doesn't have nav but i never use in built nav systems as they're never up to date. I have a Brodit phone holder so always use google maps or the likes. The other plus of this stereo is the quality of the bluetooth module as it has new technology in it, I always stream my music from my phone so thats a great addition for me. I'll grab a photo later.