Via Aqua aquarium chiller question

Hi, guys
I've been running my reef tank for 4 momth now. Tank size is about 80~90
gallon including a refugium, and it has 2X150W metal halide lights.
Recently, my reef tank is suffering from temperature problem. Now, the
temperature goes up almost 84 degree.
So, I've been searching for used one, and found 1/4 HP Via Aqua(Polar Bear)
CC25 chiller.
In the spec, it says it can pull down 10 degree for 80 gallon. However, I'm
wondering how it is overrated.
If anyone has some experience on it, could you tell me its real performance?

Thanks,
Sungwon