Looking at prices in your country, i would go for RX 470. Noticeable difference in speed between 470 and 480 is when 480 have 8gb of memory. Since both of your cards have 4gb it's just not worth it to go with 480s
Now that you bring that up, I have a question:
Which Setup would be better?
6x RX 470 4GB with 1000w PSU
OR
6x RX 480 8GB with 1200w PSU