They also sound rubbish and have a pretty dire GUI, the latest ones have a nicer front end, but as soon as you delve into browsing tracks or contacts it looks like it is being driven by a ZX Spectrum!
My choices would be....
£300
App Radio, if you have an iPod, even better if you have an iPhone or Android phone.
Clarion VX402E Nice little double din unit.
Sony XAV601BT - This is like the app radio but works with mirror link, so Nokia phones and the Galaxy S3. Looks quite nice and meant to sound OK too.
£400
Clarion NX302E - Mechless doubin din media and nav. No cd drive like the App Radio, but who uses CD anyway?
Pioneer AVH-4400BT - Another media player but with the advanced app mode as well.
Gives you a CD/DVD player as well, at the expense of a smaller screen. Also not as clean looking as the app radio.
£600
Pioneer F940BT - Pioneers new App radio with built in nav.
Clarion NX502E - Nice media unit and it has nav, it adds a CD/DVD player as well over the 302E but it also has far more features like more audio outs, better amps, customisable display colours, better EQ etc. etc.