I'm looking to get into mining. I already have one rig and it is performing decently, but I feel I need more.

I heard ETH's mining difficulty is getting harder and some people are switching over to mining Zcash instead. I'm currently running 6x RX 480's dual mining ETH/SC.

I want to build another 2-3 mining rigs, and want to make sure whatever I build will not decrease in performance mid->longterm. Would it be wise to build an Nvidia rig and mine alternative coins (other than ETH-based currencies) instead of building more AMD rigs?