Help on buying car video!

:)I want to buy a car video player gps navigation for my car and one of my friends recommend me this,he said that the products there are good, and there are various models of car’s GPS. I went to have a look, everything there is so cheap, so I’m worried about the quality of the products. Should I believe this? Is there someone once buy things there? Who can give me some advice? Are there any other good choices? Thanks a lot!:confused: