They tend to use the current 5.1, 6.1, or 7.1 setups, Software such as Protools or NUENDO are used to mix the audio effects with the music, as well as place the audio to separate channels. The process takes an enormous amount of effort as the audio is like taking each pixel of a picture and placing it by hand and ear.
As far as Equipment goes, they have the standard L,C,R, LFE, and depending on the size of the studio have LR, RR, SBR, and SBL but if its a larger studio they might use doubles of those channels similar to a movie theater. Also if you look at soem really good Studios they use multiple brands to test on to make sure of clarity and uniformity.
~Bob