I'm not sure that all Zhaolu mods are created equal, but the one I mentioned above was modified by recording engineer Da-Hong Seetoo, who said of the Zhaolu: "the original power supply was too small and too close to the circuit", and that the Oritek mod "had no head room and distorts a lot". I'm not certain of what his specific mods were, but I recall that the unit he upgraded had a huge external PS and sounded very good to me. I was not hearing it on a familiar system, however.
Haven't had the privilege of hearing a Filburt modded SF DAC, but the positive remarks around here are very intriguing. Do they ever come up for sale on Ebay or A'gon?