No. If you cancel your service you still have to send the Speedstream 6300 back to Sympatico like any other modem. It still belongs to Sympatico. The $69.95 fee is only an upgrade fee, not a purchase price, and is non-refundable. A penalty of $180 will be assessed if you do not return the modem promptly after you cancel the service.
If you already have a wireless router, there's not much point in getting the Speedstream 6300 unless you want Sympatico to support your home network.