Sorry. Wrong unit. It’s actually this one he has, but it must be a pre-USB version:
http://artproaudio.com/art_products/signal_processing/usb_audio_devices/product/usb_dual_pre_ps/
Looks like +48dB.
Like I said, not used this, but I’ve been using a pair of ART preamps in my studio to amplify control signals. Running 9 years now with 0 issues.
EDIT: Just saw the other ones you posted. The powermix should def have you covered, at least +27dB. And you get 2x2 extra inputs. Or any of the others.