I assume this means you are using a Nucleus into the old USB Stream device from PBD and are going into a PBD, Nagra or BAT DAC. I am very familiar with that converter. If that is the case, you may get some modest benefit from upgrading from the Nucleus as it tends to be a some what noisy device but it won't be huge as the PBD unit takes that noise away. A streamer in the middle is unlikely to have an impact. The biggest impact would be upgrading to a PBD streamer but that is not an inexpensive proposition as the MPS-X is $11.5K.
I am obviously one of the small number of PBD dealers in the US.