obviously budget and warranty are a major factor then cos you cant cut wires.
I would suggest upgrading the front speakers and adding a subwoofer. its all about personal taste. what music you listen to, how often and how loud would you like it?
also, whats you understanding of car audio? U a beginner or have you done an install before?
theres a few guys but i would be wary of some of them being more expensive than the Midrand JHB area.
Where in PTA are you? There's some guys in the North but a bit pricey
In centurion there's XXX car audio, bought a few tings from them but did not like the installer's attitude. But Zeyn is cool.
House of Sound near Old JHB Rd Subaru. Dunno if Vinod is still involved.
In midrand there's Tremor Audio-always willing to give you their time and good prices. Speak to Jules
In Benoni there's Sounds Limited-very helpful guys, also loads of experience and willing to bargain for prices.
There's a guy in PTA who does a good job. I don't know the streets name, but it's a 1way coming down, parallel to the dti / CIPRO building. Basically if you come from JHB's side and go past CIPRO then turn left at the next robot, and left immediately again he's on the left hand side. I think further down the road is / was a Toyota garage with some guy's name on it.