Lookout for a 2nd hand Zenec.
They're made in Germany and are designed for the MK5/6 platform (no cables etc needed and support canbus features). Such a difference in sound from the RCD300 too.
I got mine for ~£50 and has bluetooth, SD card, DVD (not the Nav model).
Ones with Nav are the ZE-NC2010 and ZE-NC2011. They usually go for around £150, the older model I have less than £100.