I have owned the Octave and used it with the Cynosure USB cable (which I owned at the time) and the Diverter HR (which I owned at the time) the BEST USB-->SPDIF converter I have ever heard.., along with that I installed the AMR fuse in the Octave. Was it good. HECKS YEAH!!!! It was good. One of the best sounds I had heard and as someone who has heard the $90K CH-Precision dac at a friends home, I would say that I would MUCH prefer to listen to the Octave/Diverter HR combination. Now having said all that I will state again as I have in other posts that the Octave is NOT in the same league as the AMR...period. I wanted it to be better because it is less expensive (not by much when you consider the Diverter is about $3K alone) but it simply could npt deliver the goods like the AMR DP777. If you have not replaced the stock fuse in the Octave with the AMR fuse, you have no idea what the Octave is capable of, yet and still it is out-gunned. Now, lets be fair... it is a roughly $1k dac that I think beats up most dacs out there regardless of price.
The AMR either direct into my Graaf GM 200 Graaf Modena or my Thaumaturges or via my MFA Ref or Baby Ref simply outperformed my Octave in the areas of naturalness and flow. Even my (then girlfriend) immediately chose the AMR as the goto device).
Lately I have been downloading hi-res files (just bought Glad Rag Doll / Diana Krall) and that dac is just as killer on my hi-res as it is on well recorded RB material.
I have not heard the Hex... I was going to purchase one, but honestly I have been so pleased with the level of sound I am getting now that I am in no hurry. Perhaps I will find someone who lives near me and get a chance to hear the Hex.
I now use the DP 777 with the ifi iUSBPower finding that is better than the Dynex hub I found and used to use in front of ALL usb dacs including my former Diverter HR as it simply makes them all sound more natural. The AMR DP 777 was the least affected by the hub but it did improve it a bit. The iUSBPower went even further.
Just my 2 cents.