Hi graymic, welcome to the RME forum.

A few general considerations. As far as I'm aware, only the Cranborne Audio 500 ADAT offers the possibility of being digitally connected to a recording interface via ADAT. It is €1800 pricier than other models that simply handle the housing and power supply of the modules.

Assuming that you intend to record in double speed, you would need a recording interface with 2 free ADAT ports. The question now is how many additional analogue and digital I/O ports are needed for other purposes. It would be best to create an Excel table and calculate the sums of the types and quantity of analogue and digital I/O required.

Thereafter, you can plan better and decide which recording interface would be best for you. If it needs to be USB-based, an 802 FS or UFX II might be sufficient. I wouldn't recommend starting with a Digiface USB here because it lacks the types of I/O that one wouldn't want to miss in a flexible studio: MIDI, Word Clock, and perhaps a few analogue ports where the number of ports on the device doesn't change even at higher sample rates (double speed).

Buying too narrowly doesn't make sense either; buying and selling audio equipment can be cumbersome. If the devices differ in port layout, you can't simply import the TotalMix FX routings you've worked on meanwhile into the new device and have to set everything up again from scratch.

If you want to have a broad setup, my recommendation is to consider a UFX III because it offers a wide range of connections, enough analogue ports, and useful features like DURec and Autoset. With a UFX III, you also have the final opportunity to compare RME's high-quality analogue ports and microphone inputs against a setup with Lunchbox and 500 series modules, which are expensive.

The UFX III has high-quality microphone inputs comparable to a 12Mic, and the converters of the analogue I/O ports are those of the well-known Reference Converter ADI-2 Pro FS. RME is known for transparent, high-quality conversion. Therefore, you can benchmark this excellent conversion quality against 500 series modules that likely follow a certain "vintage vibe" and colour the signal. The question is what you want or what you prefer.

As a guitarist, you will also like the Instrument (Hi-Z) inputs of the UFXIII which are fantastic. I am also a guitarist and have my guitar plugged to the UFX III instead to the amp, to record also the guitar signal. The UFX III acts also as parallel effect loop for my stereo setup with Lexicon PCM 81/91 and two Marshall combos.

The UFX III is definitely the right foundation for your setup, and based on this device, you can make further decisions whether you prefer the transparent conversion quality of RME or if you prefer the sound of the 500-modules.
It could also be that you want both.
Whatever way you go, if needed you can get easily more analogue I/O by expansing your setup via MADI to connect either preamps (12Mic) or analogue converter (M32*, M-1610 Pro, ..).

What's also possible, to use the UFX III as a mobile recording interface and to connect amp modellers to it for e.g. stage use. A powerful recording and mixing solution with DURec either as a tape deck in stand-alone mode or for backup recording when being used together with a little Windows PC or laptop.

The remainder of your setup could stay in the studio, connected to MADI-based converter, then you only need to unplug the MADI cable from your UFX III to use it for "mobile" purposes.

Having one rock solid UFX III is definitely better compared to using multiple recording interfaces. The latter makes routing trickier. Either you have to route through the DAW with higher latency (RTL) or you need to provide connections between the devices to exchange a few channels for quicker routing and for clock synch purposes.

Other advantages of UFX III, flagship interfaces can usually get new features more easily in terms of FPGA reserves. See the last RME additions of Room EQ, Crossfeed, triple SPDIF: https://forum.rme-audio.de/viewtopic.php?id=38691

If you have enough analogue I/O ports, either on the UFX III or by adding a converter via MADI, then you can use the less expensive lunch boxes without ADAT and would have an additional major advantage. No A/D conversion by the Cranborne Lunchbox where we do not know exactly about the characteristic and quality of the conversion. Then you can use here the proven RME converters.

In this blog article, you can see my setup:
https://www.tonstudio-forum.de/blog/ent … iii-en-de/