Amp for outside
N2B,
You have come to a good place to learn about HT equipment. You wont find too many Bose fans here, but you have to start some where.
Concerning your Sony receiver, most have the speaker A / B terminals wired in series or parallel. Thus, when you run speaker A AND B the amp sees a low (or high) impedence which can effect its performance. For now, I would recommend using speaker A OR B so that you don't damage the receiver.
You should be able to connect an inexpensive outboard amp to the TAPE, ZONE2, or other line level output on the receiver using the red/white RCA connectors. Check online for inexpensive amps from AudioSource. Anything more than 50 Watts should be adequate for your outdoor speakers.