That is a kick ass gaming set up, lol. I do have to say I'm jealous!
Yep the lugs are 21mm, pretty sure 12x1.5 is right although I'm not totally sure anymore. If you're using your stock lugs you don't have to worry about the 12x1.5 part. Just check to see that the taper on the base of your lug matches the taper on the lug hole in the wheel.