Currently, I am running with only one GPU. I am planning to buy 2 more GPU.

Hello @sathishnp83.
I mainly mine Ethash type coin. I have only one GPU.
I got 29-30 Mh/s.

Thank you @philipma1957. I will follow the altcoins thread from next time as I am new here.
Can you please confirm which power supply (watt) do I need to buy for running these 3 GPU?

I want to put 1 Asus ROG rx580 GPU and 2 Sapphir NITRO RX 590 GPU in my ROG STRIX Z370-H GAMING
 motherboard.
I have already the Assus ROG RX580 GPU.
Want to put another 2 GPU.
a) Can I put 3 GPU in Z370 H
b) Do I need to choose Asus ROG RX590 over Sapphir NITRO RX 590 as I already have asus rog 580