I went ahead and ordered a Raspberry Pi 2 and a Hifiberry Digi+ board with SPDIF outs. They should be here next week, and I'll let you all know how it goes.
For those who were interested, I got my Pi 2, Digi+ (transformer version), case, and coax cable today. After some trial and error, I got it set up with Rune Audio. My system is now as follows:
USB Western Digital Passport hard drive connected to powered USB 2.0 hub->Raspberry Pi 2 with i2s Hifiberry Digi+ board->Schiit Bifrost Multibit via coax->Vali 2 with Siemens E288C NOS tube via PYST RCA cables->Dyanamat modded HD600 headphones with SurfCables balanced cables and balanced to single ended adapter.
Prior to this, my chain was the same except I was using a mid-2013 Macbook Air to feed the Bimby via USB, without a Wyrd or Regen.
Using this new setup, which cost a little over $100 for the Pi, board, case, and coax cable, I can tell that the background is much quieter. Pretty darn black all told. This allows me to hear little details that the Macbook obscured, like the needle touching the groove on vinyl rips I have. This setup also has more dimensionality and better instrument separation. It's very easy for me to identify each element within a track now. The Bimby is already very good at this, and the SPDIF connection has made that aspect even more pronounced. The low end also feels tighter, so while it had heft before, now it also has more definition.
While I can't speak to the Mac Mini setup that Mike discussed earlier in the thread, since I haven't heard it, this Pi2 combo is hard to beat for a little over $100 US. If anyone is even curious, I suggest giving it a try. It's an inexpensive and relatively easy way to get away from USB, and avoid all the decrapifiers, reclockers, and expensive USB->SPDIF converters.