I have just bought the Sony STR-Dn1040 a/v receiver with the intention of using my existing SONY BDV-E380 speakers. However these are only rated at 3 ohm input impedance which would need 80 amps of power according to my calculations. I do have a set of Logitech Z5500 speakers with 8 ohms input...

Anyone know why my receiver would only be taking 2.0 stereo from my set top box? I'm scouring settings on the cable box (Comcast/Cisco) and the Sony, but I'm not seeing that one magic switch to flip. I'm using all HDMI connections. Any ideas? Thanks!