The converters are similar, though not identical. Neither of the two has a particular "sound quality" by design, so whether or not you will hear a difference, and which, is something only your ears can tell you.
Everything else is subjective - one listeners "warm" may be another's "dull"....

I'm not aware of any scientifically valid double blind converter comparison that includes these two devices on any forum or so.

Regards
Daniel Fuchs
RME

Hi,
The ADI8-QS does sound better technically but when you get into high quality AD/DA devices you tend to suffer from diminishing returns.

The differences in audible sound quality is very tough for some one even under even the best conditions to detect with just their ears reliably.
When there is a noticeable difference it almost always ends up being level mis-matching, pan law, clocking. In some cases some "high -end" AD/DA intentionally color or alter the sound. Usually in some attempt to emulate the effect processing nature of a analog tape or a tube driven circuit.
Thankfully RME does not do this as part of it's design. 

RME designs their product to be as transparent and uncolored as possible at their given price ranges. You are paying for a different feature set of the ADI8-QS over the UFX.

Whether or not you need that feature set I think is the question.

I have no idea what current gear you have that you want to replace, upgrade or add on to so I cannot give  good answer as to which would be the best choice for you.

Thanks Chris

Good thread happening here Welcome Ryan!

Thank you for explaining this in more detail!  I am very satisfied with the ADI-8 QS'. The options it has were also why I bought them. Just wanted/needed some clarification on the actual converters between the two explained, which you did so well. Cheers! Now I can comment on them when compared.
Anything more you can add would be appreciated. For example. I would love to have panning laws explain more in detail?

Next question please:  Does the UFX have the same pre-amps as the Micstacy? I'm also told they do. Can someone please clarify this?

Hi Avening,

I've thought about getting an Orpheus more than once. Even debating it again. It would be impressive if the UFX sounds comparable. I would love to find out if they are indeed close enough for both the convertor and the preamps.

Good to hear your opinion on them coming from PT. I have an old Pro Tools Mix plus system here that is in the closet. I miss Pro tools  software but not the hardware at all.

Looking forward to more discussion in this thread? Anyone confirm the preamps being the same as the Micstacy?

Thanks for that info.

Can you comment on the analog stages of the UFX?  I know that the UFX employs an 8-Channel Cirrus CS5368 IC on the AD stage and a Burr Brown PCM4104 on the DA, but what do the analog stages before the AD, and after the DA look like?  (Obviously very high level ... not asking you to post schematics or anything).  Can you walk us through?

Only reason I ask is that many other manufacturers use similar converter chips, but employ different analog designs making the interfaces sound different from each other.  I know RME takes the approach of not adding anything to the sound, and I'm just curious as to how that is accomplished.

Thanks.