I have the ozone on my Cal Spa 867b I don't remember it being called the Puresilk Ozone but maybe I just missed that part. I think my last 3 or 4 hot tubs had the ozone, seems pretty standard to me and yeah for $185 just get it.
It doesn't really lower the chemicals you will use, but it does keep the tub cleaner. "They" always seem to tell you what ever it is it will reduce your chemical usage.. good sales ploy. I don't use many chemicals in my tub anymore any way, pretty much just bleach (chlorine) and muriatic acid.
When do you get that tub? And you will love it I think, I love mine! Heck I'm heading out there right now!