Thanks Jeff, the channels are going from the analogue outputs of the organ to the Mac, so I suppose I should buy an M32 pro AD. But since the ufx+ is already connected to one instrument, I need to buy the complete equipment new, so an audio card and an expansion. I am also looking to keep the equipment as little voluminous as possible because I need to arrange it into the organ console case and there is not so much space…

Sure, will explain better. The three instruments are located in three different places in my house and are all independent from one another. Each instrument is connected to a different Mac and has its own audio system. When I started to apply an external reverb system to the first organ, I already had a fireface400 (pretty old but still perfectly functioning) and needed to add some inputs to receive the 12 available outputs of the organ. I bought an ucx II and set up an aggregate device. It works very well, latency is acceptable for live playing. I applied the same concept to the second instrument but this time I bought the ufx+ with 12 analogue inputs to match straight away the 12 outputs of the organ too. Now, with the new organ, the third, I need 20 inputs because the instrument has 20 analogue outputs. Hence my request for advice about the best solution. Hope this makes sense.

The maximum sample rate I use is 48k, so the digiface usb should be ok. Should I then couple it with the m32AD? Budgetwise it’s like buying two UFX II so I wonder what solution would be best. Is it correct to assume that digiface usb + m32AD would be more stable and reliable and two UFX II would be more flexible (should I use the same equipment for other purposes in future)?.

I use Apple Mainstage for live performances, Logic Pro for recordings and I add reverb with different plugins, mainly from Liquidsonics

I have spent an important amount of money for the last instrument and therefore I do not want to save a few bucks and risk to compromise the quality of the whole chain. I do not know the specifics of the analogue outputs of the organ but I doubt it uses esoteric DAs. For my first organ, initially, I used a presonus card and was not particularly impressed with it, everything sounded kind of muffled. Then I bought the UCX II and I could perceive a clear improvement in sound quality. But sometimes I also wonder how much objectivity is there in my personal evaluations and what role expectations play on a device that costs much more and must sound, accordingly, much better. I like RME because my fireface400, bought back in 2008, has been rock solid ever since, so I also like the reliability of a device after the initial installation. When I switch on one of my instruments I just like to play, not think about failing drivers, components and so on.

Now it seems to me that setting up an RME system with 20 channels will cost minimum 3500/4000 euros which is not little money. At the same time I would not like to spend half that money and then regret the purchase because of poor performance.

So, in order not to let this post hanging without a final answer, I would like to close it by saying that I bought a M32 AD PRO and a MADIFACE XT. All works fine.
Thanks to those who tried to understand the ‘weird’ needs of an organist who clearly does not know much about audio equipment.
All the best.