Quick question: are spirits affected by stun damage (stun ball, gel rounds, etc)? Do you have a page to reference, or is it more of a "it doesn't say they aren't so they are"? Thanks in advance.

From what I understood... Spirits have both a Stun Track and a Physical Track, just like most (all?) other living entities... Sorry, I do not have a page number to reference for you however...

Pg 176 SR 3 main book

An astral form suffering Deadly stun damage is disrupted.
A disrupted astral form immediately disappears from the astral
plane; astrally projecting characters return to their physical
bodies (regardless of any barriers separating them), white spirits
vanish entirely. The character is unconscious (at Deadly stun
damage) and must recover normally (p.g. 126), A character who
Is disrupted in astral combat must immediately check for Magic
Loss (p.g. 160). A spirit disrupted in astral combat cannot reappear
in astral-space or the physical world for a number of days
equal to 28 minus its Force.

Basically, at least for spirits, physical and stun damage have an identical function. You fill up a damage track (doesn't matter which, but you got to fill one of them up), they get disrupted. That's pretty much the score of things.