Sony Pictures Television produced Breaking Bad[1], and Mad Men was produced by Lionsgate Television [2](who also produced Orange is the New Black). Netflix doesn't need to buy AMC, they just need to outbid other companies when buying content. Which is exactly what they did for House of Cards, they beat AMC and HBO for the rights[3].
[1]http://en.wikipedia.org/wiki/Sony_Pictures_Television#Shows_...
[2] http://en.wikipedia.org/wiki/Lionsgate_Television#Production...
[3] http://en.wikipedia.org/wiki/House_of_Cards_%28U.S._TV_serie...