Do standalone digital-to-digital EQ and Room Correction products exist? SPDIF in SPDIF out

Looking at a DAC that has digital S/PDIF (RCA) In/Out called a "monitor loop"..

The idea is to insert your component of choice in the digital path to apply EQ or Room Correction.

I cant seem to find any of these simple digital-to-digital S/PDIF EQs out there.  Many seem to be overkill for this application with their own built-in DACs, multitude of other connections, etc...

Products that almost fit this scenario, but not quite, are:
- Schiit Loki (analog only)
- DSPeaker Anti-Mode 2.0 Dual Core (optical only)

you may want to look at the pro audio side of things. but your most likely going to find similar things that do much.  

I agree that would be a great product. simple room correction DSP in a box. it could be digital in - analogue in with digital out and maybe an analogue out too. 

This would allow the use of room correction with out replacing whole systems that you may already have invested considerably into.
The miniDSP SHD Studio would be my pick. It has Dirac, arguably as good as any DRC system and better than most.
There's' a miniDSP nano which works.
+1 for the miniDSP SHD Studio. It's very flexible and has a lot of functionality in addition to PEQ and Dirac Live. I don't think you can beat it in terms of bang for your buck.

A couple of more expensive options are the Trinnov ST2-HiFi or DEQX PreMate.
Along with some of the recommendations so far, persistent googling has turned up the following options:

- miniDSP SHD Studio All in One Streaming processor with Dirac Live Digital Room Correction ($899 USD)
- miniDSP DDRC-22D All digital Dirac Live correction DSP ($725 USD)
- miniDSP OpenDRC-DI All Digital Floating Point Room Correction DSP (FIR Filters) ($325 USD)
- miniDSP nanoDIGI 2x8 B All Digital Fixed Point EQ DSP ($170 USD)
- Z-Systems RDQ-1 Reference Digital Equalizer ($1500 USD used)

The  DDRC-22D seems to be a good choice with Dirac support.  The SHD Studio is a good choice also but I dont need the streaming.

How destructive these are to the signal in a HiFi application is yet to be seen.  I read that the cheaper nanoDIGI may introduce some phase distortion for mid-range EQ adjustments, which is over my head but certainly a red flag.

Anyone here have any experience with them?
Background: I have used various DSP units over the years, including the TacT 2.2X, Weiss EQ1 mastering equalizer, the full SHD (with DAC) in our living-room (second) system, the Classe CP-800, and the Anthem STR preamp. Unfortunately, I haven’t used most of the specific units you listed.

My listening impression is that DSP technology (like DACs) is improving, so to minimize unwanted effects on sound quality, I’d get the most recent and powerful unit. The miniDSP SHD does its DSP at 96 kHz, 32 bits, while I believe the older miniDSP units are 48 kHz. That (and its many features) would make the SHD my choice. It sounds great in our second system, but as I’ve not run it in my main system, I can’t comment on absolute sound quality. I do participate in the miniDSP forums, and no one has complained about the sound.

The Z-Systems unit is well regarded and easier to change settings on the fly. However, it has not been made for many years, and I don’t think I’d pay the price for it, rather than get a new SHD. Z-Systems is no longer making this sort of equipment.

I hope that helps!