looking for head unit replacement only? rm100 to 250 not much choice cept cap ayam

500-600 ish.

consider a used unit if you're not going to use long and not willing to spend much

if you want a better quality HU, then opt for second hand (or maybe parallel imports if you dont mind warranty issues)

that alone iss good enough.

Aiyo. 

The most basic sound system consists of a player (HU/headunit), speakers (components or 2-way/3-way) and a sub (active/standalone). All cars have these things (ok.. maybe not a sub).

If you have a car that has a built in stuff like the VWs then be prepared to replace the entire dash (middle panel) with an aftermarket adaptor to fit aftermarket players.

Since your car is just a Kembara, replacing the player is just a matter of taking out your old one and installing the new one. There's no such thing as whether it can "fit your car" or not. If it's a complete panel player like those taken out from a Camry, it will not fit. If it's an aftermarket from Pioneer, Sony, Alpine, etc.. then it'll fit for sure. Just a matter of with or without an aftermarket bracket/adaptor.