My audio-card is a simple Behringer U-Control UCA200 (shows up as USB audio codec). I have no problem using it with my main DAW, I can select both it's outputs and inputs, and it works great.
But Reason doesn't let me use it for it's audio inputs

As far as I know, it's not possible to feed a Rewire slave audio.. and Soundflower is acting strange, I can't use it properly on Mavericks. Basically, Rewire or not, it's not working.
So instead i've been playing with the amps in my main DAW.
Anyone could help me out ? Thank you !
From OS X preferences, it is selected as an audio input : it doesn't help (in Reason)