Fireball is an absolute ripper of a machine but as Nino has mentioned, you can almost forget about owning the EM version. Dont discount Fireball Classic which is the SS version, it just doesnt have the zipper flippers which is a shame.
There are some good value for money Gtb Sys 1 machines as well. You have the popular machines like Joker Poker and Genie but Sinbad is a good game as well. I bought a project Sinbad a fair while ago that I was intending to tidy up and sell but I have still got it and still enjoy playing it regularly.
Another good EM machine is Jacks Open. Your biggest problem will be finding nice examples of any of the machines already mentioned, most of them are tucked away in private collections and rarely come up for sale.
