I've got first hand info for you. I've driven it with 496 HO Mags & it is very easy & super stable to drive. Paxson (son of the Cobalt co. owner) has one on Grand Lake with 600's & it will run in the low low 80's. Needs very little trim and responds well to what you want it to do.
You can't go wrong with a Cobalt. I think they are the nicest boats out there in terms of build quality & support.