1) Go with the HDMI to your TV if it's the only way to get an HD signal to the monitor (otherwise, I'd think about using the component connection), and use a digital audio to the receiver (I prefer digital coax to Toslink, but only because of a slight advantage in durability).
2) I like 10 ga Belden from Blue Jeans cable for speaker wire: the chart says that 10 gauge is overkill in most cases, but its only $0.57/foot, so why not?
3) I wouldn't use a composite hookup, even if your DVD player isn't capable of progressive scan you ought to consider using an S video or component hookup for your picture.
Bryan...HTH...