The crossfire will definitely beat an slk 230, remember that the crossfire IS an slk 320. Benz wouldn't make the more expensive slk320 slower.

Specs:
192 hp - 215 hp Crossfire wins
200 tq - 229 tq Crossfire wins again
Don't quote me on this but, i remember hearing that the crossfire is a 100 pounds lighter than the slk230 (that's 3 strikes the slk230 is out).