Also, you can look in your local newspapers to see if there are any arcade auctions going on; they're a great place to pick up used cabs, often at really great prices (that's how I got mine).
Be sure to keep an eye to any arcades in your area as well - they're often looking to get rid of older machines in order to make way for the newest games, and they just might be willing to part with an old MVS system that might not bring in the money like it used to.