to use the other channels, yes you will need more speakers. if only 2 for sure, all you need is a 2-ch amp/receiver.
the speakers will decide about 80-90% of the audio sound quality of your system, including the subwoofer.
newbie here. I want to buy a onkyo 7.1 receiver and 2 bose speakers preferably wireless ,to keep it clean.
What happens to the power when it is split into 2 speakers.Can the speakers handle it? Or should I have to buy more speakers.