Apologies for not posting much at all.
The project is stalled for now, as I had both my proto boards sent to a friend in the US to save on shipping (as I planned to have him ship many things at once). I had everything planned out until I found out I couldn't pay for the shipping label with my PayPal then it started falling apart from there. In addition to that, he can't send them on with his own money due to very complicated reasons so I pretty much have run out of things to do without touching the boards themself.
That said, I'm thinking about the different engineering challenges and compromises that is involved with the use of one board verses the use of two. Use of a single board means that differential output has to pass through two opamps via a single-ended to balanced buffer and it'll have a noticeable (adverse imo) affect on sound quality due to the opamps. This can be somewhat remedied if I swap the opamps but it adds another element of failure for the manufacturing process and then we'll have a whole new debate over which opamps different people want. This can be somewhat fixed if I stick a socket there but it will add noise and then I might as well not change the opamps.
However, having two boards adds its own challenges too. I have to parallel each of the digital inputs and supply power supplies to each board (I'm not sure what effect paralleling the same supply will have as per the latest plan I have), connect the serial lines to each other and increase the height of the enclosure significantly to take the two boards. This is without taking into account any other mods I may or may not perform for sound quality (as detailed on the blog) as twice the number of boards means twice the failure rate.
The reason why I'm troubling over this is because I would much prefer to offer either SE or differential options only as offering both would mean having to increase the price across the board due to smaller production runs meaning more expensive per-unit costs. Overall, I still haven't decided on whether to use dual or single boards (especially because an extra board also increases the price by a large chunk).