While we don't support using 2 AudioBox 1818VSLs simultaneously on the same computer, you can get an AudioBox 1818VSL and a Digimax D8 to access all 18 inputs onboard the AudioBox 1818VSL. You'll plug 8 additional inputs into the D8, connect the D8 to the 1818VSL via an ADAT connection, and then you'll be good to go!