If you have some Big Bucks to Spend, then go for Alpine Store at Boat Basin (Next to Jans Broast). There the RCAs will cost around 4K and fitting etc will cost around 2K.
However, if you want a cheaper and effective solution, you can go to Tariq Road (Behind McDonalds). The shop just next to McDonalds & In front of Graveyard. The Guys name is Sajid and Umair. They do good work and have good stuff too.