According to the website the ERR3702 water "refiner" also includes a charcoal chlorine filter. It does seem like a slick unit. It even has a salt level indicator. Still a lot of money. You might also look at
Discount Water Softeners if you are into self installation and maintenance and ever decide to make a change.
Honestly though, I'd just pipe in the pool to what you have and se if it's manageable. I really don't think it will be that bad and what do you have to lose, you can always put it back the way it is now or put in a larger system. Low risk test.