I'll take a stab at this
First you should know that your receiver will have crossover settings for all the speakers in your system other than the subwoofer. These settings are available if you set your speakers to "small" rather than "large" in the receiver's setup menu. All frequencies for all speakers below this crossover setting will be rerouted to the sub. Frequencies above this crossover setting will be sent to the appropriate speakers. You can set different crossover settings for center, l/r front, l/r surround, and left/right back surround.
In your case the Sony main speakers are rated to go down to 40hz, which is wildly optimistic but does indicate that a crossover setting of 80hz or so will work well. The polk satellite speakers only go down to 95hz so the crossover setting should be set higher for them--maybe 110-120hz. All frequencies above these crossover settings will not be sent to the sub. For this reason you can set the sub's crossover knob anyhere you want as long as it's above the highest crossover setting you're using for any of the other speakers--even all the way up to the 300hz setting as nothing above the crossover settings you set on your receiver will get to the sub anyway. Most all receiver mfgs recommend setting the sub's crossover knob all the way up when using the receiver's bass management.
One benefit of using bass management (rerouting bass from mains/center/sat speakers to sub) is that it relieves the reciever of the heavy power load necessary to reproduce low bass frequencies--that load is assumed by the amp built into your powered subwoofer. This frees up power from the reciever for the mid-high frequencies for less distortion at higher volumes. This is why it's not a bad idea to go ahead and set the crossover for your speakers higher than the minimum rated frequency response of those speakers.
The human hearing apparatus can't localize frequencies below 100-120hz very well at all so there's no harm in rerouting those to a single subwoofer---it won't affect the perception of surround sound at all.
Basically, set your sub to about half it's volume setting and turn the crossover knob all the way up, run Audyssey, then check the results--if the sub level is automatically set below about -2 db or so, turn the volume knob on the sub down a bit and repeat the Audyssey setup until the receiver does set the sub level at 0db plus or minus 2. Then go in and manually set any speakers that the receiver sets to "large" to "small" and set crossover for the Sonys to 80 or so and the polks to 110-120. You don't need to rerun Audyssey again after doing this,