Yeah, you guys are nuts. Games largely don't have high enough quality audio to benefit from high end equipment in the first place, and secondly, do you really want to be the guy who shook his monitor loose because he had the bass turned up too loud on Pooyan.
Real games usually had a sinlge 5" or 6x9" speaker that cost all of $3.
Also, be real careful using car speakers in an arcade cabinet. I replaced the demolished subwoofer in my old Turbo with a car one, and immediately gained a lovely fade across the red spectrum on the monitor that didn't go away until the red went out on the thing completely.