It was my understanding that GM retired the supercharged 4 that formerly powered the Cobalt and adapted the turbo 4 used in the Solstice/Sky RedLine for FWD...and since that engine was making 260hp in those models that should turn the Cobalt into a fairly stout performer.
I like the looks and style of the G5 over the Cobalt but a 260hp turbo 4 would move the G6 fairly well I think.
I prefer the G6 over the G5 especially in GXP trim.