Well, I've had my Octave and USB to SPDIF devices for about 10 days now. In short, with the right set-up I am truly surprised -- I didn't think digital could sound this good, this vinyl-like. My ripped CDs have more life and soul than I thought possible.
I ripped the CDs using XLD/CD Paranoid to make sure I was getting bit-perfect rips. I bought a Mac Mini to use as a dedicated music server, put a solid state drive in it, 8 GB of ram, and put my music on a connected external hard drive (because the music files are too large to fit on the SSD drive). I spent a while on the computer audiophile forum to set the system up.
At first I was playing the files with the iTunes add-on program Bit Perfect. It sounded better than iTunes on its own. But as soon as I switched to the free trial of Audirvana Plus, it was obvious that this was a huge jump up. My wife who often thinks my changes are splitting hairs, immediately said it sounded much better. I haven't tried Amarra or Pure Music yet.
Since there were 30-day money back guarantees for both devices, I bought two different usb --> spdif converters: the Audiophilleo2 and the Stello U3. They have both been burnt in for more than 50 hours now, but probably less than 100.
The Audiophilleo consistently sounds much, much better than the Stello. The first thing I notice is how much more dynamic it is. I do also notice more low-level details on the Audiophilleo. I was worried that this might be the sort of thing that at first seems better but with time comes to seem unnatural. Far from it, the Audiophilleo feels more natural.
In some ways what is most impressive to me is that I have no fatigue at all. When I tried playing CDs through my Oppo my ears hurt after half an hour. I had been pretty happy with my Play Station 1. But this set-up is clearly in a different league. More life, more detail, clearer highers and lows -- just better. And I can listen happily all day long. I am having a lot of fun going through listening to my favorite CDs in much higher fidelity.
So anyway, I will report back after I've had the system for longer, but this is what I'm thinking so far.