You need to check the gauges of each type of wool and work out how much they differ. One firm's chunky might be another firm's ultra chunky. On the other hand you might find you need to use two strands of chunky together.
I haven't seen many yarns thicker than king cole's ultimate super chunky, very satisfying to knit on 15mm needles and beautiful colours
http://www.kingcole.co.uk/knitting-yarns/new-releases/the-ultimate-super-chunky.html