The old saying 'you get what you pay for' springs to mind.
I recently changed my stereo as was tempted by these chinese units that look OEM and also come packed with features. After searching and searching i decided not to ge one. One BIG reason for my, which may not bother you, was the return policies for them, and if it breaks, it goes to china for a repair, even if its a week old, and i wasn't happy with that idea.
I decided i didnt need sat nav due to having a tomtom, so went for a JVC KWAV60BT. The kenwood sat nav units are nice but youre looking at £550 plus for them.
Have a serious think about what you need rather than what you want. I wanted sat nav, but i'll use it twice a year if i'm lucky, so its a waste of money for me!
But make sure you google the models of these chinese ones, and check youtube for videos too!