How many channels do you see yourself needing for both recording and mixing? I don't really see either option RME being a wise choice for you.
For instance, if you intend on running 16 stereo stems out through hardware to mix, you'd need 32 channels of A/D and D/A. If you're going with the MADI face then you'll need something that supports MADI, on its own it has no analog I/O to do what you need (it has 2 in 2 out but you'd presumably need something for your monitors). The UFX only has analog I/O to do like 4 stereo pairs of HW inserts, so you'd need to expand with MADI/ADAT/AES etc.
Whatever you decide to go for would be a fairly considerable expense to do what you have in mind. I'd try and get as much analog I/O as you can in a single device than trying to chain multiple devices together. Doing that is fine if you already have bits of gear that you need to use, but if you're starting from scratch I wouldn't recommend that route.
I think Antelope are pretty dreadful as a company but depending on what you're willing to put up with an Orion (somewhat affordable) or Galaxy (64 channels, but £7000 odd). If you want to go with a better brand (and honestly, I would not recommend Antelope to anybody) then be prepared to spend £10,000+ (and factor in the extras like d-subs, patchbays, racks, cabling, and all the other HW gear itself).
If you're looking at doing stuff expandably, I'd probably look at something Dante based these days as it's a lot more widely adopted than MADI.
