Thanks for the replies folks. It's good to get some perspectives about this. So I'm OK with using copies of cards for the time being instead of buying a second core set ($200 is a pretty high buy-in for a game I don't even know if my group will like). Are there any other issues folks have run into GMing for larger groups? Scaling adversaries for example?
I'm sure this has come up already on the forums, but I haven't had any luck finding it. The box says 2-4 players. My gaming group has six people including me. Is it impossible to stretch the game to four or five PCs? I assume not, and that the major issue is to have enough cards for everyone. Have people tried playing with larger groups? What adjustments were required?