I spend an inordinately long time looking for the elusive E-painting with the last portion of the code we need, only to realize it's in the very first room you enter upon entering the Recreation Deck. Silly me.
Also, we finally break into Tier 4 psionic powers, which gives us Invisibility and Protoss psi-blades of doom. Unfortunately the rest of the powers on that tier are kinda cack, but that's just more reason to look forward to Tier 5!
Ah yes, and I also went on a little adventure off-camera to unlock the armory on the Med-Sci deck. Turns out there's a log on Deck 4 that you have to find, hidden behind a chair in the lower section behind Bulkhead 23 (not far beyond the charger and the replicator where we bought the Reycler).
Then you go back down to Deck 2, input the code and find...
...An assault rifle, an EMP rifle, a stasis field generator, combat armor, two batteries, three frag grenades and some standard pistol ammo. Not that great unless you somehow missed the assault rifle on Deck 3, but at least I found a couple hidden Cyber Module caches along the way that I missed before (both of them in the starting area to Deck 6, ironically enough. One was in the trash can near the upgrade units and one was hidden behind the long crate just before the bulkhead).