I think your Bridge II card is flawing your listening. When we did testing, the Bridge card totally trashed the sound quality no matter what mods were done. I would not recommend using the Bridge card as one could never get the great sound these DS’s can provide. With our External Power Board one can A/B the sound difference by just turning off / on the external supply (the internal supply takes over automatically).
The panel of listeners we had could hear NO difference between the internal supply and external supply so it’s not just my opinion. This was also done with the XS4400 transformers as well as our nickel transformers.
The external supply makes no difference in our listening tests however the nickel transformers along with the Vocm mod makes a huge difference.
We had one member with the external power supply, XS4400 transformers and the Vocm mod that used it for several months. We changed his transformers to the nickel ones and he was blown away. He also could not hear any difference between internal supply and external power supply.