I have an ONKYO 905 if that matters.
Is the higher bitrate lossy sound available from the coax digital output, or just HDMI?
lossy dts on DVD: 768kbps or rarely, 1.5Mbps
lossy DD on DVD: 192kbps to rarely 448kpbs
lossy dts 'core' on BD: up to 1.5Mbps typically (DVD can do that)
lossy DD in the companion track on BD: up to 640kbps typically but I've seen 448kbps
These can pass via SPDIF. But you are limited to 5.1.
There are other threads already asking about the differences between lossless and lossy scattered around AVS. We just keep repeating the same over and over. The latest (apart from this thread) is this:
Also worth noting: there's nothing "HD" about it in a typical Blu-ray because most BRs use 48kHz sample rate, the same in DVDs, and not usually what people would call high resolution audio (88.2kHz to 192kHz).
My own view is the difference between lossless and lossy is subtle (almost nil with dts) and more in the nuance than night and day differences and very much depends on content (speech/effects/type of music) and volume. Hence it'd be very hard to do proper trials or give generalisations.
Audiosceptics accept audio trials using 25 people. A recent Oxford study with over 353,000 patient records from 639 separate clinical trials shows for every 1,000 people taking diclofenac or ibuprofen there would be 3 additional heart attacks, 4 more cases of heart failure and 1 death every year.