OK, so here is the final report.

In short, TB connection did not improve things drastically but did bring UFX+ closer to Konnekt 8.

The gap between TC Electronics Konnekt 8 and UFX+ is now the smallest - they are almost on par, Konnekt 8 being a fraction ahead. It's quite subjective because now both have the same limits in terms of buffer size / latency but it feels that UFX+ has a bit more dropouts than Konnekt 8 on higher regimes.

When I chose the flagship UFX+ I was hoping for the best latency in class, reachable on a usual, universal station like mine (i7-4790K, Asus Z97a, 32GB RAM, 1TB Samsung Pro SSD). I did not care about MADI or huge number of channels, I was interested in a very basic - yet the top notch - functions.

Now it's obvious that UFX+ does not deliver better latencies than 10-years old Konnekt 8 and if you are looking for that you'd better look elsewhere (does such device exist at all?). Now I wonder whether it's Konnekt 8 so good (strange) - or UFX+ not so good (makes even less sense). Perhaps, RME UFX+ shows it's potential in sterile conditions - in studios, on specific and optimized hardware, etc. However, for a single home user, in mixed environments UFX+ doesn't impress - may be due to the high expectations. May be I should have bought external preamps + F/W-driven UFC, who knows.

At the same time, all other UFX+ features are very solid and much more advanced than Konnekt's. Frankly, these two devices cannot be compared in this area, for example
- Konnekt 8 has not even a single shade of the power of TotalMix
- Stability, well, yes - Konnekt is less stable )
- etc, etc, etc

Despite UFX+ has not met my initial expectations, I am still quite satisfied. Moreover, I'd probably buy it again if I had not have it )

That's your perception, nothing else.

I have conducted many tests on various OS, BIOS, and "transmission scheme". Yes, the tests might not be mathematically correct but sorry, I am a home user, and not a audio interface reviews publisher. Well, as for me, I spent enough time and money trying to make RME UFX+ work at least comparably fast as Konnekt 8.

My hardware is perfectly OK, it's still more advanced than majority of home studios have. Have a look at numbers I posted earlier and you would see that my system is in fact quite close to Ramses's one.

My mistake was to assume that the RME flagship is better than 10-years old interface (in terms of latency, there is indeed no point to compare other features). Here you made a clear statement about that, confirming what had been posted by me.

You are correct. yes, I have an Excel table with various numbers measured but that's not a strict research, I did that for myself to not get lost in various setting combinations. If you remember, I performed tests on clean Win7 & Windows Server 2012, I did multiple of CPU & BIOS tweaks - and tested ALL of those in Sonar.

You saw the numbers, your system and mine are quite close. This M/B and hardware are NOT in black lists, it's a very solid hardware. This system has been performing very well on mixed tasks, including audio production.

I tried USB 2, USB 3 on dedicated port, I bought TB card - no much difference. At the same time, Konnekt 8's latencies have been solid no matter what: number of VMs running in background, BIOS and CPU settings. I had no idea that all that stuff could influence audio before I installed UFX+. With Konnekt it all did not matter, it just worked.

Please! I wrote that one of the test series had been conducted on a clean Win7 OS without any WM, in fact without any software at all except for Sonar and such. Also note that Konnekt has never paid attention to whatever VMs are running or "installing too many things onto your systems". It just works consistently, period.

Those mysterious hardware / software incompatibilities again!.. Anything can be explained by them
My point is simple: if 10-year old interface's latency is good on this system then a contemporary flagship cannot be worse than that.
If one interface just works and for another you have to go through insane quests of choosing the right harware, tuning configurations, etc, the question arises: what interface is then a flagship, really?

Having said that, I admit there is a probability something is wrong with my conclusions or my hardware. However, considering the number of tests I performed, the number of various transmission scheme used, the various hardware / hardware settings involved I do think that the main conclusion is valid:

RME UFX+ does not offer better latencies than Konnekt 8.
This is what MC had confirmed in his post. "An impresssive, technological achievement". I am fine with that. As I mentioned, it was my mistake to have wrong expectations. Perhaps I should have bought dedicated preamps and a much-smaller-number-of-channels interface as it looks like the larger number of channels affects the latency in a negative way.

Ramses, you could be right, why not?.. I am also tempted to test another F/W / USB interfaces, may be I'll get one and see the results. May be indeed UFX+ and Konnekt 8 are top-notch and the rest is far below.

When I get to the point to upgrade my system I will revisit this thread in a couple of years. It will be a good test.