I wouldn't use a PCI card anymore, because the number of mainboards with PCI slots is very limited.

In general the RTT times are very low for every RME product, but to get really the lowest RTT times I recommend you to take a recording interface which has all required I/O ports already on board.

The reason for this is that when connecting AD/DA converters via digital ports such as MADI or ADAT, you need to add their AD/DA conversion time to the RTT.

The DAW only shows you the RTT up to the recording interface (what the ASIO driver reports to the DAW). This does not include the additional time required for AD/DA conversion from devices connected behind.

You can see this from the following table, which I put together some time ago.

I haven't had an AIO at hand, but the card will surely have very good values and you would have the advantage that the card is connected directly to the PCIe bus.

Times for AD/DA conversion depending on the sample frequency you can luckily find in the RME handbook.
It's great that RME delivers all these valuable informations :-)

You can nicely expand the AIO using digital I/O ports:

As the AIO offers 3 digital ports (ADAT, SPDIF, AES) you can easily expand this unit with i.e.
- ADI2 Pro FS get high end AD/DA conversion (via i.e. AES)
- either Preamps or AD/DA converter via ADAT

The AIO also allows analog expansion, see RME product page / handbook.

In regards to expanding the AIO with an ADI-2 Pro FS now or in the future:

1. This blog article shows, how nicely the ADI-2 Pro FS integrates into a RME recording environment: https://www.tonstudio-forum.de/blog/ind … our-Setup/

2. And in terms of RTT latencies you are also on the save side, because the ADI-2 Pro FS AD/DA converters
have a very low latencies:
- AD          : 0,11ms @44.1kHz, 0,10ms @48kHz, 0,06ms @96kHz, 0,026 @192kHz
- DA Sharp: 0,14ms @44.1kHz, 0,13ms @48kHz, 0,06ms @96kHz, 0,029 @192kHz
- DA Slow  : 0,12ms @44.1kHz, 0,11ms @48kHz, 0,05ms @96kHz, 0,024 @192kHz

Advantage of this combination is to have the AIO with TMFX for routing and the ADI-2 Pro FS on top for reference quality (speakers, phones).

No, it's very clear thank you!
I was mostly waiting for someone who had some (more) measurements from the series of cards I was interested in. The two measurement of the AIO card I have found are: https://www.gearslutz.com/board/music-c … hlight=rtl
at 5,283 ms at 64 samples 48kHz

and from the former DAW-bench forum which is offline now. Vince measured it at 4.263ms.

I have an ESI ESP1010 that I measured at 3.923ms. It's puzzling that low-cost cards perform "better" in this regard, but I also understand that the drivers for the AIO-interface is made to account for the much larger track count that it can handle simultaneously.