qts,..the PSU will be fine. When you pull air in under the PSU to the CPU, then you have devices lower in the case that get starved for air.
Your method to solve a problem could create another problem
Having the PSU and case fans pull air out of the case, vents the heated air out of the case, instead of mixing it up inside the case.
By having a large exhaust area high in the case, the cooler air will be drawn from the lower case openings and thus cool the entire system, and not just the CPU.