MegaDoomer

I am picking this up for my game group to play. I'll be getting the core, multiplayer expansions, and all 3 boosters. I noticed the core comes with 2 decks so I assume every player needs their own deck. It doesn't seem like the multiplayer expansions comes with any decks. So will I need to buy 2 extra decks for 4 of us to play, or is 2 enough for everyone? Or does the expansion come with the decks and I have just missed where it stated so? Please help. Thanks in advance.