Where should I go from here with my digital front end?

Yep, you have correct connection protocol. If going fiber route do linear power supply for at least last FMC, lps for both best. Also may want to consider moving to Sonore OpticalModule and OpticalRendu vs the generic, well worth the premium. I'd estimate your setup will expose the improvement.

Get a ViaBlue EP7 B4 Christmas. Triton Cables is closing - liquidation sale.

Silver plated. I upgraded and sold my Supra.

@emil 

The cat cable is the last thing to change. Why not try a Linear power supply? The power supply on the U1 and the U2 is the weakest link. Check out SBooster.

Thanks for the info on your system. Looks thoughtfully assembled with some good choices.

I don’t know, you have a pretty good setup. If you have $1K. I would save it and wait until you can invest in a better integrated amp as your next step. In the mean time I would work with your setup, room treatments. Enjoy what you have. Assuming you have a good quality power cord on your amp.

You can get small incremental improvements by fiddling with your network. But there are so many opportunities. All opportunities must be weighed… interconnects, power cables, isolation, set up, components.

Add this to your optical set up.  It made a nice improvement over the wall plugs.  It has two cables and can power both FMC’s.  Optical made a big difference for my system.