The Stock stereo system on the boxster is horrible. I basically changed the dash speakers as well as the door ones. I put in the dash the Boston Acoustics Pro 6.4 tweeter and in the door I installed the Boston Acoustics Pro 6.5 sub. As for the amp I put in a Rockford Fosgate 500 A2. The head unit stayed stock. What I did to get the amp installed to the stock radio was to buy a plug that gives you 2 RCA outputs. Many installers do not know about this plug, but it can be bought from Continental Imports.

Here is a picture of the amp, mounted in the front and the Boston Acoustics Crossovers.

Here are some pictures of an AMP and Sub Mounted in
Martin Dareff Car.