Best performance saloon / couple

[PompeyPaul]

What would you consider the best buy for around 30k and why? On the assumption of around 1,000 miles a month and that it is a mixture of motorway and town driving, with the fun being weekend country roads.

I'm assuming MPG and General running costs will be similar across the board.

BMW M3, M5, M6 or C63 AMG?