This may have been beaten to death already, but I can't seen to find any definitive answers.

I know that there is a $2k upgrade from the standard 3 speaker ACR stereo to the 18 speaker high performance audio, and that seems like a really good deal. My question is around the upgrade from the 12 speaker GTC ACR system to the 18 speaker system. Looks like the price is the same - is it really worth it? What do you get with those extra six speakers? The option price is still $2k, and that seems steep for what appears to be a six speaker upgrade kit...

Thanks!