Your receiver may have a total of 220 watts which is about 70 watts per channel at 6 ohms. Most HTS systems have wildly exaggerated power specs so the only thing you have to be concerned about is the impedance of the speakers. Your Onkyo may not work with speakers below 4 or 6 ohms. Check the specs on the AVR and the HTS.
You may not be able to use the subwoofer from the HTS since most of these have the sub amp in the main unit and all AVRs don't have a sub amp built in. You would need an external amp for the HTS sub or a self power subwoofer to replace it.