Totally agree... mix and matching AMD/Nvidia is not trivial as depending on what miners you use it might not be so easy
For instance Claymore's Ethereum mining would work on both Nvidia & AMD however its Cryptonote (XMR/ETN) is only AMD, you need a separate software for Nvidia
I would recommend trying to get 2 AMD RX 580 it's more profitable than the GTX 1060 however not by much (for the past few months atleast)