It took me five years to find a C37. There are so many great EMs it is hard to zero in on just one or you will let a bunch of good ones slip by in the process. I would suggest that you either pick a type of game you are looking for or have a list of at least ten titles. Then buy one when it pops up at the right condition and the right price. Unless you have a good tech on standby I suggest buying one that you can play a game on without a bunch of trouble before buying.

Edit: Outer Space and Orbit are great playing games.