Stop it. Just stop it.
Stevenson gets KTFO by Froch any day of the week.
His power is formidable - more so than Froch's own - but won't matter against Froch, who will walk him down and end him. It's a question of punch resistance being on two completely different levels. Not to mention, while Froch doesn't get as cute as Stevenson he's arguably got the more effective high-level skill set and certainly has oodles more high-level experience.
Easy work for the Cobra.