I have a Denon receiver so I don't know if the same answer would apply to Onkyo but here goes. Denon customer support told me that my front speakers had to be configured as "small" speakers because if I configured them as "large" the system would assume that they could handle all the heavy lifting in the bass. I reconfigured as "small" and the subwoofer started working. Hope that helps in your situation.

A passive speaker requires an external amplifier. This is the common configuration most people are used to. An active speaker has a built-in amplifier and these are usually subwoofers such as the Klipsch or Polk available at Best Buy. They connect to line level outputs from your preamp or a single LFE output. Since bass frequencies require far more amplifier power than mid-range and highs, the powered (active) subwoofer relieves a burden from your amp. They offer a crossover to send low frequencies to the subwoofer and higher frequencies to the main speakers. An active subwoofer also reduces Doppler distortion of the higher frequencies because cone travel of low frequencies is greater. Yes, this is the Doppler effect that makes train whistles rise then fall in pitch as they go by. The same thing happens to your mid frequencies if a single speaker cone handles all the range.

This unit connects to the internet either wired or Wi-Fi. I have it auto connect to my 5GHz network. You can connect to Netflix, YouTube, Amazon Prime, Google Play and to your smartphone. You can also download firmware updates wirelessly.

I recommend going to your Best Buy store and listen to the demo setup. It lets you push buttons to select among several speakers and you can make your decision. Consider how big your listening space is.