Crossover & LFE hz help. Polk S10 & S35, Dayton SUB-1500

I have a 3.1 system. Front speakers are Polk S10, center is Polk S35, and sub is Dayton SUB-1500. What should I set the speakers and LFE crossover at?

Polk says the frequency response of the S10 is 67 Hz - 40,000 Hz, and the S35 is 53 Hz - 40,000 Hz. However, I know a lot of folks say Polk may not accurately represent how low their speakers go.