. Instead, we had to hook up the...gulp....composite audio cables
Ok as stated this is a no issue - toshlink or composite doesn't make a difference just get a good cable and route it to the Receiver.
The box you have is much better than the old box and they also have the DVI turned on so if you have DVI input on your TV then get a DVI cable and hook that up and your picture will improve. TWC is great here in Charlotte they just suck at informing their customers, but their service is great.
This forum is a mix of Direct-TV, Dish, Cable, Over-The Air (OTA) antenna customers and you will read lots of posts that doesn't affect you (nor me) and just ignore those and let others answer those.
Post any other issues and people will help you out. Also on the box hit Settings then the A button (I think) to go in and change aspect ratios, output format etc for best setup with your STB