Froch would struggle at 175, (same way Golovkin would struggle at 168 vs Froch). If Groves can put Froch down, Kovalev certainly can and probably stop him. Kessler might take Kovalev the distance though...if he fought smart.
I think kovy beat both of them. Kessler fightnwould be a massacre. He is way too rigid and predictable to have any chacne, Froch would be more competitive, cause hes tough and he has a weird unorthodox style, but kovalev would catch him eventually.
Kessler gets banged out but don't underestimate Froch here. It's a tough call between him and Kovalev due to his absolute toughness. I think he takes a better shot than Kovalev for sure and can hang in there and take some of Kovalevs shots to land his own.