Check earlier in this thread for the eBay external cards. Veneet, for example, found a box on Amazon that works well and he cut out a couple of holes (contact him for help). That’s at…
Also look at the R47 desoldering photo in this thread (I think) for those cards, which is necessary to prevent the PS Audio dacs from throwing up a de-emphasis flag (suggest reading the entire thread).
For the Oppomod card, see gazjam’s thread for the result…
and the bulk of gazjam’s install photos at…
and videos about opening the case (and install of Oppomod’s PSU and CD/DVD player mod in a 203) at