Did you go into the menu of your current cable box and see if you can set it to PCM?
What benefit would a newer cable box give you (more chennels, higher resolution but your already 720p already right)?
I'm not seeing spending 150 when it doesn't solve your problem. For 50 your done with this but maybe flipping a switch. For 80 your done with this...wait where did that apple tv come from? I thought it was just TV and AAE. So now maybe you need one DC07 and two DC03, 110. Plus each new component provides a new feature, nice.