All of these cars are extreme high-performance cars, but if it came down to picking one of these cars, which will it be? I am willing to wait for the "perfect car" if it means a year. It is a huge investment for me. If possible, please support your answer with reasons (I recognize that the M3 and C63 may not have some or any specs released, for they haven't been released).
Mercedes C63 AMG, the new one.

I would say it depends on your age. Audis and BMWs (to me) are aimed a little more towards younger, business casual types.. Mercedes more towards the older more conservative crowd. All are awesome, though. I am a little more biased so I'd go with the BMW because my boyfriend has a Bimmer. My ex had a new Mercedes and he's stuck-up and thinks he's better than everyone cause he has $$$. The R4 seems a little over-priced and I don't think many people would know how expensive the car is, of course, if that doesn't matter than it doesn't matter, either way it's a beautiful car and you rarely see them. BUT I still think you'd get the biggest bang for your buck with the M3.

im a fan of the m3. i have a 2002 bmw m3. oh wee. love it. but i'm not sure about the 2008 model. doesnt look that great.

2nd would be the 2007 Audi RS4. black. that would look nice.