I just picked up the deco and I’m loving it too so far, its awesome for guitar and it works perfect with the octa and digitakt.
As an adat expansion for an interface it adds four above average preamps plus four extra line level inputs so you can add pre amps or use it like I’m using it now with my octa and tape machine taking up inputs 5-8. I got it for tracking drums at first but it’s so flexible I’m still coming up with ways to use it. If you have a small interface with an adat expansion jack it’s awesome and it can grow with you once you get a better interface or converters. I will say that I’m still looking to get one really nice pre or maybe a stereo pair but even after I get those I wouldn’t get rid of my 4-710d.