A:
Thank you for the Question!
You can certainly use a 7.1 receiver with the Acoustimass 6III Home Entertainment Speaker System. Be advised that this system will provide you with 5.1 surround sound. If you want to achieve 7.1 surround sound, then you will need to purchase additional Bose speakers, see recommendations below, to connect directly to your receiver.
You would not be able to use Bose cube speakers, like the ones that come with the Acoustimass system, but there are a variety of other passive Bose speakers that will work.
(This answer applies to the Bose Acoustimass 10 IV and Acoustimass 16 Home Entertainment Speaker System as well .)