thanks, looking forward to seeing if you find any info. I've searched multiple sites and can't seem to find any more detailed specs than what is listed on the Onkyo site.
Since both are Onkyo lower mid range AVR I would say the 13 lbs weight differences are due to:
- The 808 has a much larger enclosure, that means more steel=more weight.
- The 808 power specs is approx. 20% higher, so it likely has a larger transformer, more capacitance, larger output devices etc. Transformers are heavy so the transformer in the 808 could be a few lbs heavier.
- The 808 will also likely have larger heat sinks, and if they are made of steel then that adds weight also.
- There is a possibility (just a possibility) that the 708 may not have much heat sink at all but rely on a fan for cooling, and the 808 has a much larger enclosure so Onkyo may skip the fan and use heat sinks exclusively, in that case the heat sink may have substantial weight. Again, on this point I am purely guessing, both of them may or may not have a fan.
The 808 is definitely going to get you about 20% more power but that may be hardly noticeable especially if you are going to be listening to mostly two channel music. So if you want to stick with Onkyo, the 708 seems like a better fit for you. The $250 you save now can make it easier for you to add a two channel external amp. That's when you may gain some real meaningful power.