Well with 81F water to chill with, I would suggest considering a pre-chiller to get colder chilling water, rather than spending on a plate chiller (you can look into doing something akin to a jockey box for the chilling water supply). In the winter I set a bucket with water outside overnight and use a pre-chiller and cheap pump for re-circulation to minimize the amount of water used (avoiding an ice slick), but I am blessed with 56F well water pretty much year round.
Of course you can stir the wort with the chiller to get into the 80's faster, just that you are limited in the lowest the wort will go without putting it into a freezer chest or fridge....to get to pitching temps.