> Most affordable would be best.
> Something with at least 2 mic preamps. Will have it go through the ADAT In.
Least expensive is ADA8200 for under €200.
> Need it to be RME so that I can still use Totalmix FX with it
No, simply a preamp that can be connected through ADAT
> Also, with an RME, how much extra latency can I expect?
Transfer through ADAT has no significant/noticeable latency compared to transfer through USB depending on ASIO buffersize or converter latency.
The latency that you will get on top is the converter latency of the connected preamps for A/D (and for D/A if present). But converter latency is compared to RTL over USB much much lower.
See here typical values from one of my blog articles:
https://www.tonstudio-forum.de/blog/ind … 8-RME-UFX/
It has already been pointed out, that ADAT can carry 8 channels at single speed (44.1/48). The ADA8200 is limited to single speed, but gives you everything for a low budget: preamps, line in, line out.
In contrast to that RME's least expensive preamp is a Octamic II for €1279.
Not sure but assume that this exceeds your price range.
But if you want to have a RME preamp, then this would be the least expensive solution to upgrade through ADAT.
If 4 preamps are enough for you as you said, then we can make a cross caluculation.
If you add the cost of BBF Pro FS and Octamic II: €1279+698 = €1977
For a little lower price you could get an UFX II for €1879 with four really fantastic Mic Preamps with 75dB Gain range, that are flexible as they can also be used as line or instrument inputs.
Furthermore a lot of features and possibilities to expand: 2x ADAT, 1x AES, 2 phones outputs, 2x MIDI I/O, DURec, Autoset, Full implementation of FX chip...
Then later maybe an ARC USB on top if you want to have a remote for TM FX control room.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13