Focusrite Clarett OctoPre by Leveuho
This box is a really great expansion for my RME UFX interface. Using it mainly with line ins for my synth gear, but also tested the preamps for vocal tracking purposes.
There are cheaper options on the market, true, but believe me, this is the best device you can buy in this price range. Just pristine sound with more than solid s/n ratio and dynamic range, stable work for long studio hours, days and weeks, easy controllable via front panel.
"Air" function works really great on vocals, adding really pleasant brilliance, though I still prefer to keep my vocals more balanced and rounded with ART VoiceChannel + Mullard tube.
I don't actually like 6 inputs in the back, would prefer to have them all in front, even if using patchbays, but this is just my personal preference.
Probably the best ADAT device 700 bucks can buy right now (though I haven't tested Arturia AudioFuse!).