Not had a chance to open the two up and look at them side-by-side... I based my statement on differences/similarities on the "feature charts" but you are certainly correct about the weight difference upon further inspection. Having said that, just going on the feature charts listed on the site I found the following
- NR1010 & 50.4 have Neo:X, the NR818 does not.
- NR1010 & 50.4 advertise a Push-Pull amp design... NR818 does not have that "checked off"
- NR1010 & 50.4 have digital crossover processing, 818 does not
- NR1010 has VLSC and 50.4 & 818 do not
- NR1010 & 50.4 share the same 1080p upscaling (818 uses Marvell instead of HQV)
Not making any comments on the relative importance of these differences (obviously the weight, presumably dominated by the difference in the power supply, is significant). Just saying that the processing "guts" of the 50.4 appear closer to the 1010 platform than to the 818 platform. I do agree, however, that the backpanel of the 50.4 much more closely matches the 818.