Asked and answered previously here in the forums. No, they are not rated correctly for the Ascent. There are some mighty fine threads in the Wheels/Tires discussion area that detail what wheels will work with the Ascent.
Please do not. They're not even remotely close to the load rating that the Ascent requires. I've spoken directly to Subaru's wheel manufacturer, and the WRX/STI rims are custom designed for the WRX/STI line, to meet that car's much lower load rating needs.
The STI wheels need to and are designed to carry a max of 1,102 pounds per wheel (plus a safety margin added to that)
The Ascent wheels need to and are designed to carry a max of 1,648 pounds per wheel (plus a safety margin added to that)
NOT taking into account the safety margins that Subaru and their wheel manufacturer add in before determining the load rating, that leaves a full ton of load rating difference between the wheels (546 pounds per wheel, for a total of 2,184 pounds). The safety margin is a percent of max load, btw, and isn't anywhere near the 50% necessary to bring an STI wheel plus safety margin, to max without safety required for the Ascent - so, that doesn't help either.