Hold the phone - a very close second place would be the new Lincoln MKS or Taurus SHO as far as bang for the buck goes. A few simple mods to those cars and they are pretty quick too. So it just depends on how much you want to spend.
It also depends on what kind of feel you are looking for. These cars could not be more different in their essential character.
The MKS/SHO is a nose heavy, understeering tank with a V6/AWD, and the V has a traditional RWD/V8 rumble. It is also physically smaller and lighter than the Ford duo.
If you live in a wintery climate and/or need a truly cavernous interior, the MKS/SHO makes more sense. If you like the way a V8 sounds, want to leave two black stripes on the tarmac, and enjoy the occasional power on oversteer in your 4 door, well, the Caddy is the obvious choice.