That's a lot of questions. To get d-link you would need to step up to the 3910 or higher. Since these new denon models have D3, you will also be able to pass sacd, dvd-a, etc.
You would not only need a discerning ear, but some very good equipment to notice a difference between D3, IL or HDMI. Realizing, of course, in order to pass D3, you need a Denon receiver and player, to pass I-Link, you need a Yamaha player and receiver so equipped, and with HDMI, you need HDMI so equipped models. So we are not really talking apples to apples with all the possible permutations. That is, it is not possibly to test the signal trasnfer on a Denon 5805 and 5910 via I-link, and conversely, the same is true for yamaha's flagship models. These signals are passed purely in the digital domain, so the transfer is impeccable to begin with.
I have said this numerous times before, and I will write it again, you will be very hard-pressed to better the signal transfer over a high quality set of analogs (for sacd), or high quality optical for movie soundtracks. If you're trying to keep up with the latest and greatest, you'll never keep up, because as soon as they came out with HDMI 1.1, they announced HDMI 1.2 for sacd. Denon Link is obviously proprietary, and has been around for about 5 years. I-link has been around for a while as well. HDMI just started taking off less than a year ago. Marketing, competition, etc. I am more concerned with high build quality (for longevity) and superior audio and video in my equipment than I am with the latest greatest interconnects. You have noted some pretty good equipment above, so if that's your price range, I would buy them in conjunction with a good quality set of interconnects (whatever they are, component minimum for video), and never look back. Cheers.
