Whats your max budget for that ?

I would get the RME UFX II (in budget) or even better the UFX+ (a little above budget).

These flagship devices have the more up to date converter even a better analog section compared to the old flagship, the UFX. The UC is not bad but the design is from July 2009 according to Thomann, thats 12y.

I see some advantages for you with the UFX+
- Three possibilities to connect to PC/Mac: USB3, Thunderbolt, USB2 (without MADI). Use what works best.
- TOSLINK cable is limited to 10m per standard usually 16m still work with RME devices
   With MADI you can build a serial connection (ring structure) between usually up to 8 devices, where the cable
   between each of the devices may be up to 2km long, so if you need a larger in-house cabling, e.g. for a 2nd or 3rd
   HiFi, then you have more options

Both new flagship interfaces (UFX II and UFX+) have stronger and more modern phones outputs (even two!).
Device can be operated fully stand-alone.
You can use Pen devices / USB disks and connect it to the UFX* to perform backup recordings or to playback music.
Either for backup recordings or stand-alone recordings.
For backgrouns music without the need for a PC / streamer ...

Check out UFX+ and UFX II. I would go for the UFX+ for getting ultimate flexibility for only a few bucks more.

You find information on RME webpage and also in my blog section, the UFX+ is an awesome interface.
https://www.tonstudio-forum.de/blog/ind … 8-RME-UFX/

You can compare the recording interfaces easily using my Excel. It contains useful information from Product Page, Manuals, this forum. The blog article: https://www.tonstudio-forum.de/blog/ind … B-MADIfac/
Direct link to the Excel File: https://www.tonstudio-forum.de/index.ph … 0-08-xlsx/

Ok, I need to remove this now, thanks for the pointer. Let me explain, this was a term taken from RME product pages which was valid at that time when comparing popular recording interfaces like BBF, UC, UCX, UFX. Meanwhile newer devices appeared on the scene and you can either choose between two general options a) to choose a recording interfaces alone which offers multiple analog channels or b) a combination of recording interface with enough digital I/O ports (SPDIF, ADAT, MADI, AVB) and other devices (usually DA or AD/DA converter) behind it.

The UCX
is from Jan 2012, ~3y later compared to UC. Still good quality, but HiFi people are usually very picky to get the latest converter design and the possibility to choose between different AD and DA filter of the DAC chip. Very popular in that regards became the products ADI-2 DAC / ADI-2 Pro with converters from AKM (Asahi Kasei) that are even compareable with much higher priced products in the mastering scene, see this comparison video, where the original .wav files are available for download there: https://www.youtube.com/watch?v=bIx9tCc8gVM
And this sticky posting gives you an overview about the different ADI-2 DAC/Pro models that appeared on the market after RME collected a lot of feedback from customers and did most of the wanted modifications:
https://forum.rme-audio.de/viewtopic.ph … 06#p165706
In the latest design the converter have been upgraded from AK4490 to AK4493 and now even the Pro model has a remote.
You get higher SNR and an additional analog filter, but the changes are not audible is so far is the general assessment.

Why the proposal UFX II / UFX+?
Because it offers you (compared to UC and UCX) very good converter technology in one case to an affordable price. The UFX+ is a special case that would support possibilites for maybe interesting inhouse cabling options and extensions. But ok, no problem, if it has too many features for your taste, that you do not require then lets stay with the UFX II, it has the same analog section like the UFX+ and would offer you the mentioned price benefit. Ok, so what are the alternatives ?
BTW, $2500 equals to ~€2051 as I took the german prices from Thomann.

Option A) UFX II - Total Price: €1879
https://www.thomann.de/de/rme_fireface_ufx_ii.htm €1879
Better alternative to UC and UCX, better analog section compared to the former flagship recording interface UFX.
The device supports Class Compliant Mode so that you could e.g. use an iPAD or Linux as player.

The next options use the Digiface USB which has 4x ADAT I/O with the unique feature, that allows all four optical ports to be switched between either ADAT or SPDIF protocol. Although such a feature is not necessarily required, because the RME converters ADI-2 FS, ADI-2 DAC/Pro * are able to read the 1st two channels out of an audio stream using ADAT protocol.
Just as a note, the Digiface USB does not support CC Mode (Class Compliant Mode) so you need a PC/Mac with RME drivers like with the UC. CC Mode is supported for UCX, UFX II, UFX+.
These options might have the advantage for you, that you can use optical TOSLINK cables (which are thinner compared to analog cables) to place the devices closer to the speakers, so that the thicker analog cables can be shorter.
According to the standard a TOSLINK cable can be up to 10m long, but I made already the good experience with RME devices, that TOSLINK cables might even be 16m long (15m +1m after a TOSLINK switcher) still supporting sample rates up to 192 kHz.

Option B) Digiface USB and 3x ADI-2 FS - Total Price: €357 + (3x €699) = €2454
https://www.thomann.de/de/rme_digiface_usb.htm €357
https://www.thomann.de/de/rme_adi_2_fs.htm       €699 (3x)
Digiface USB in short: 4x ADAT/SPDIF, needs PC/Mac with drivers, no CC mode.

Option C) Digiface USB, ADI-2 DAC FS and 2x ADI-2 FS - Total Price: €357 + €966 + (2x €699) = €2721
https://www.thomann.de/de/rme_digiface_usb.htm  €357
https://www.thomann.de/de/rme_adi_2_dac_fs.htm €966
https://www.thomann.de/de/rme_adi_2_fs.htm         €699 (2x)
Digiface USB in short: 4x ADAT/SPDIF, needs PC/Mac with drivers, no CC mode.
The ADI-2 DAC FS in this setup could also act as a nice phones and IEM preamp for you.

Option D) Digiface USB, ADI-2 Pro FS R BE and 2x ADI-2 FS - Total Price: €357 + €1739 + (2x €699) = €3494
https://www.thomann.de/de/rme_digiface_usb.htm                            €357
https://www.thomann.de/de/rme_adi_2_pro … dition.htm €1739
https://www.thomann.de/de/rme_adi_2_fs.htm                                  €699 (2x)
Digiface USB in short: 4x ADAT/SPDIF, needs PC/Mac with drivers, no CC mode.
The ADI-2 Pro FS R BE in this setup could also act as a nice phones preamp for you supporting either two phones which also enables for headphone comparison or alternatively the use of balanced phones (IMHO overrated, you're mileage may vary).

It seems overkill to me to use the large RME multi-channel devices for your task. When you "just" want to add an option for FIR (which might not be the answer to your audio needs anyway necessarily, but that's another topic) you could use other places to insert the covolution. You can use the free Equalizer APO to run system wide convolution on Windows and just keep using Mini-DSP in your current setup. I don't see the advantage to change that from your description. If you "just" want a new good 2-channel AD/DA the Babyface could be all you need already.

Or you could go other active ways like using Hypex or other amp modules where you can have the crossover / filtering. Upcoming versions will add FIR as well, btw.

Or if you want to go the route of a new device, but keepinig your amps using Aurora could be what you need. Bad is that AFAIK they are currently not available due the AKM chips not being available.

In general for your needs I think you'll likely get "better" advice to achieve your goal on the DIY forums or Audiosciencereview and the likes. BTW, you asked here for devices. I would state the actual problem. Then you'll likely get the better answers :-)