Alternatively, you could sell the soundcard, and replace it with one that has more i/O, and especcially adat connections for expanders later on.

I quite like this approach, also because your daw can double up as a midi router and audio patchbay, that is quickly reconfigureable and has preset saving/instant recall.

i guess some of the digital mixer double as a soundcard, not sure about those in the 500 euro category.

Cheap analogue ones tend to have a lot of noise and colouration, and ones without soundcard functionality do not allow to record more than one stereo track, maybe a few tracks using auxes, monitoring outs or alternative outputs. Well, 4 mono or two stereo in the case of your current Volt 476