Righty - so it seems like your AA is doing pretty much all the work here - it actually looks like quite low settings overall.
Could you stick up:
-Your aa min and max
-Do you have “use dmc threshold” wicked on or off, beside your aa min / max? If so what number is in there?
-Stick up the reflection subdivs you’re using on floor, ceiling and wall materials?
-What GI method are you using?
-Also could you put up a reflection pass, MTL glossiness pass, a raw lighting and a way global illumination pass?
Just trying to find what’s really noisy in the scene.
The light coming from the left of the scene - what’s that from?