First thing to watch out for is that voltage rating. Is the ESC rated in volts only, or LiPo packs? A fully charged LiPo cell can be 4.2v, which would put you at 33.6v. Some ESCs tolerate higher voltage with no problem, but some go POP if you go a tenth of a volt over.
With that voltage, 84A is lots of headroom, so you've got no worries there.