The HK has 5.1 pre-outs & 5.1 analog inputs, but the Onkyo does NOT.
The HK has 720p Upscaling, and the Onkyo does NOT.
The HK has 2 HDMI-1.1 inputs, and the Onkyo has 2 HDMI-1.3.
The HK does NOT have TrueHD/DTS-MA, but the Onkyo has TrueHD/DTS-MA.
So if your HD player (like blu-ray since HD DVD is dying rather rapidly
) has internal decoders (like the upcoming ETA-Spring Panasonic DMP-BD50), then I would get the HK-347, which IMO has better sound clarity/quality and more honest power output than the Onkyo-605.