He is not entirely wrong or right, I guess his reply was cause op is inexperienced so he will never hit the consumption you would hit. I do have experience and I can say 1000w is more than enough but you need skill to optimize it. Also the prices you said are spot on, around 2100 usd, 5 x rx 580  will give you around $4 per day which in turn you will get back your money back in 525 days or 18 months to be precise but your system will have to be 24/7 and without problems and that is impossible, so count it as 24 months to get your money back. If you buy eth right now, in few days you will get 500% or more hehe and no problems at all.