2 box setups either using Deus platform or infact any of make are specialised machines,they sound super sexy but they will come with a reasonably high cost attached as most things that are Deus related are.They can go ultra deep but mainly on large targets and the larger the target the deeper they go,but for say single small coins or infact any small find i doubt very much that they would pick them up and certainly not at any depth.
The market aimed for these machines would be say WW2 artifacts and hoard/cache and 'NOT' for general everyday detecting use,would demand for this addon system be stellar i doubt it,of course i could be wrong but saying that going by sales of normal 2 box systems they are a very limited market.
Of course this is just my personal opinion,i do use a 2 box setup for site specific detecting,but if i am honest its not used all that much,but as i like to think that all it would take was just one decent find and that could pay for the detector/s many times over.