Receiver configuration
Sin,
Great list of receiver and speaker options. The sub is probably the weak point, but you can't beat free.
No problem with a 7.1 receiver. In the receiver's manual or auto setup it determines your speaker configuration (5.1, 6.1, 7.1, etc.) and does the audio processing accordingly. These days, only the entry level models are limited to 5.1 Some 7.1 receivers will also let you use the extra amp channels for speakers in another room or to bi-amp the mains.