Oppo 205 and external DAC?

Yes I know. There are multiple outputs on the 205 and multiple inputs on the BDA-3. 

With my Ric Schultz modified 203, I inserted the iFi spdif Purifier, basically a reclocker and galvanic isolator into the end of the run to a DirectStream dac. I've found it to offer substantial improvement over using a Snake River Boomslang spdif cable alone, as if I had purchased a much more expensive cable. With the dac's new firmware, know as Snowmass (to be officially released maybe 11/11), the difference in clarity, size and solidity of imaging and the soundstage coming forward is substantial. It was a surprise, as I thought from reading the reviews that it aimed more at the mobile market. I didn't get the same results though running a toslink cable out of the Purifier, still using the Boomslang, at least with a Silflex optical cable (the 203 mod eliminated the toslink option, so I can't run it all the way with optical cable).

Always use 205 balanced line-out fixed for best sound quality. If your amp doesn't have balanced input, at lease have a balanced pre-amp for best result. I use a sennheiser HDVA 600 earphone amp which not only serve as earphone amp but also pre-amp. very silent and liner.

Get a highly modded Modwright Oppo 205.