Wait, it's worse. I forgot they die at -10 and have Fast Healing, so it'll take a minimum of 2 Meteor Swarms to kill a Quasit even if it fails its Reflex saves. So you're only killing 970-odd per round, minus their 500-odd replenishment, so it'll actually take 58.25, round to 50, hours to kill them all.<br/><br/>AftS is a better answer, if the DM will let you have it (there is that nasty little issue with it needing an artifact to go off each casting, which is technically suspended for SLAs though).