Yikes!
160 watts pushing stock Porsche speakers???
Unless you keep the volume way low, you'll surely blow those babies.....I doubt the stock speakers can handle more than 40 w rms.....
My advice......Pull back on all those amps, improve the stock speakers, and get yourself 1 6 channel amp or 2 multi channel amps to handle things. Will be cheaper and more efficent, and will still sound a lot better in the long run.