Don't even think about using a chainsaw on a stump !
It's plunge cutting (bad) in a stump that's likely full of rocks
(worse)

I'd hire the stump grinder.

Or if it was in the garden and I wasn't in a rush, drill and burn it on
the next barbecue as a logger's candle. X-shaped cut down the middle,
or else a few big holes broken through into each other, then stuff a
paraffin rag into the gap and and light it. The two vertical timber
faces facing each other burn pretty well, once you've got them going.
Pre-soaking a couple of weeks before with a nitrate solution helps too.