But I talked to the guy and he also said that I maybe should go for an Apogee Duet, because if I bought one of those I would never have to buy any new card, even if I build a real studio... I would surely have to upgrade from a cheaper card If I made a studio and got some expensive speakers... What to do think?
Not surely no....some of the cards mentioned are perfectly good performers as far as DAC is concerned. You would struggle to tell the difference between the output of these & the Apogee.
The Apogee is by all accounts a great card so if you can afford the budget increase & can live without the phones volume go for it.
If it's too expensive then the TC would be my personal 2nd choice followed by a Focusrite.
I would try to forget about whether you are paying for preamps you don't need...concentrate on researching the quality of the units features you will use. DAC quality & driver performance & headphone amp from the sounds of it.