Adding a battery to power the RPi makes a very worthwhile difference. I'm using the 5v out on the Ankara battery that also powers the BM MKII. I wanted to power just the USB SPDIF converter to see if that alone would make an improvement but the RPi won't recognise it so the whole lot got the battery treatment. I'm struggling to tell the difference now to my modded SB....

The SB is powered with dual ALSWR super regs and re clocked with an XO-3 Tent Audio clock plus a load of other circuit mods...I think I'll use the SB PSU to power the RPi and see how that sounds, at the moment I feel it's a little 'soft' and a touch over smooth in comparisons...it's a mighty close call though!