Not sure about current cars, but for mine, the short answer is count the speakers:
If you have 6, you have the base stereo
If you have 10 (including subs behind the seats) you have either middle or top.
If you have 10, check your stereo. Hit the music key to see if you have DSP settings. If you have DSP settings, you have the Carver top system.
GVfB has more info than you'd ever want on this. It might be in the DIY section already.