Yes a different multichannel DAC where all channels shared the same master would be best. I'm just talking about what's possible with what you have already since it has that port. But yes it would take remapping the FPGA for support.
Actually it looks like I may be wrong about that. It appears they are using LVDS receiver chips, instead of connecting direct into the I/O bank of the FPGA. Unless those chip are for ESD protection. It's not as good of a way to do it. Those chips add jitter. The Spartan 6 FPGA can be programmed as a direct LVDS receiver and sender. That's the best way to do I2S over LVDS. It also makes it possible to remap to send data out as well as in.
View attachment 22981