the main difference is the fact that hdmi 1.3 can carry the new lossless audio formats ( dolby true hd, dts-hd ma), but if you didnt go with a receiver that has 1.3 you can get those formats by the analog outs on your blu-ray.....given the receivers listed i think the onkyo 706 would be nice for the setup...i love the synergy series and onkyo...the reason i would go with the 706 over the 606 is mainly beacuse it has pre-outs if u ever wanted to an external amp to your system