I installed the 
Continental CDD7416UB-OR unit in my 2001 Boxster.  I used the 
M490 harness described above.  It works great so far and I really like its appearance in the cabin.
The only problem, though, is that when I lock the car using the remote, the horn honks once, indicating that something isn't right (like the glove box is ajar, trunk not latched, etc.).  I did notice that the instruction guide talked about a blue/brown wire that had to be isolated.  I see a wire like this in the bundle, but assumed that it would have been handled by the harness.  Has any one else experienced this issue?
Edit:  Solution posted here:  
Continental TR7412UB-OR Stereo Installation and Review