Here's an odd thought about 5 years too late:

Maybe the number of PCBs required could drop to one if it could do both ends of the job. Combine the features of both empeg-side and display-side boards into one, give each person two of the same board, but only populate the necessary transistors for each. Not only would it remove an entire PCB, but it would double the order quantity of the remaining PCB.

5 years too late, not worth mentioning, but interesting. Still trying to convince myself to take 2nd run spot number 10 for when I have a car without DIN... in 2014.