Hi Ton, The head unit is a real personal thing it will always come down to what you can afford and what your wanting from it. I would check out good audio sound stores like Monster etc. They usually have a good range of units and all the cabling required and also can fit the unit for you. Buying online is one way but not one I would choose because you can not physically look at it ask questions etc much easier going in person to somewhere, even Supercheap or Autobarn are a good starting place.
Let us know what you end up doing
KAA