Sounds like you've got it under control. As you guessed, with a 5.1 setup you'll need 5 PCA's from the 950 to the amp and an analog audio cable (RCA connectors) to the sub. Check the back of the cable box to see whether it has coax digital audio, optical, or both - the Scientific Atlanta boxes I've seen tend to have coaxial only, but the Pace HD box I have currently offers both. Enjoy!