Surround sound setup

I've just disconnected two sets of Bose First Edition surround sound speaker systems (very old) and am setting up a new system with Polk Audio. I have a Denon AVR4100 set up in 5.1 driving a Polk Audio CS1 Series II Center Speaker, 4 Polk Audio TL3 Blackstones and two Polk Audio PSW505 subs. What would be recommended for a good starting point for the crossover set points of the center speaker and the TL3's? Each speaker channel can be set independently.