ALL US CAR OWNERS BEWARE. This "upgrade" is not for our cars. This is for Non-US cars only. The "standard" audio system in the US is actually good. It is true stereo (unlike the HK) and has tweeters etc.
There are still upgrade paths your audio system in the US (HiFi/Standard being the easiest system to upgrade), but I don't really see the need and I am a self proclaimed audiophile.