I always send my clients over to a friend of mine that ended up getting a few clients their M3's for a few hundred under invoice...
Just spoke to him and asked him about P cars and he said as long as you've got good credit he should be able to get a sweet deal!
He's located out here in Miami and his contact info is the following:
Jeremy - 305-510-6563
Tell him Robert from Strasse Forged Wheels sent you over! It's worth a shot to see what kind of pricing he can get you!